Speaker 1: Welcome to the deep dive where your curiosity fuels are exploration.
Speaker 1: You send us the sources and we distill them down
Speaker 1: to the essential insights, saving you time and expanding your knowledge.
Speaker 2: It's a great concept.
Speaker 1: Today we're tackling a programmer's Quick Start Guide to Web
Speaker 1: Development Quick JavaScript by David Metusek. Our mission, driven by
Speaker 1: your need for efficient learning, is really to extract the
Speaker 1: core concepts of JavaScript and the HTML dom that experienced
Speaker 1: coders can grasp rapidly and thoroughly.
Speaker 2: And we're using excerpt straight from the book itself exactly.
Speaker 1: We'll be drawing straight from the book honestly. The idea
Speaker 1: of making this corner stone of webin or activity more accessible,
Speaker 1: that's well, that's what gets me going.
Speaker 2: Indeed, and what's interesting right off the bat is who
Speaker 2: this book isn't for. Yeah, Metusk explicitly advises programming beginners
Speaker 2: to start with Python. That tells us a lot. It's
Speaker 2: laser focused on bringing established developers up to speed with
Speaker 2: JavaScript quickly. It assumes you already have a foundation in
Speaker 2: promming principles exactly.
Speaker 1: It assumes you know what a loop is, what a
Speaker 1: variable is, and it's not trying to be the definitive
Speaker 1: JavaScript Bible.
Speaker 2: Right, No, not at all. Matustik himself points readers looking
Speaker 2: for that really comprehensive reference towards Slannigan's JavaScript the Definitive
Speaker 2: Guide a classic, right, So quick JavaScript is about getting
Speaker 2: you hands on providing that crucial initial understanding of how
Speaker 2: JavaScript talks to and manipulates web pages through the document
Speaker 2: object model, the DOM. It's a targeted on ramp, and it's.
Speaker 1: A necessary on ramp because well, JavaScript holds this unique position,
Speaker 1: doesn't it.
Speaker 2: It really does. It's the only language that web browsers
Speaker 2: understand natively.
Speaker 1: You can think about that for a second.
Speaker 2: Yeah, it's ubiquity, isn't accidental. I mean sure, other languages
Speaker 2: like Coffee, script or dark can be used for web development,
Speaker 2: but they all need a translation step, a compilation into
Speaker 2: JavaScript before a browser can actually execute them.
Speaker 1: So JavaScript is fundamental. It's the base layer for client
Speaker 1: side interactivity. Okay, so JavaScript is the lingua franca of
Speaker 1: the browser. Now Metusk brings up something called strict mode
Speaker 1: pretty early on. What's the essential insight there? What's the gist?
Speaker 2: Think of you strict that exact string as like a
Speaker 2: safety switch for your JavaScript code. It was introduced in
Speaker 2: ekmascript twenty fifteen six. Okay, by putting that phrase at
Speaker 2: the beginning of your script or maybe inside of function,
Speaker 2: you're telling the JavaScript engine to enforce a stricter set
Speaker 2: of rules. It basically eliminates some potentially problematic or error
Speaker 2: prone parts of the language.
Speaker 1: Ah, cleaning up some historical baggage sort of.
Speaker 2: Yeah, METUSAC emphasizes that for all new JavaScript projects, using
Speaker 2: strict mode isn't just a good idea, it's really the
Speaker 2: recommended standard. Yeah, so for modern JavaScript you strict is
Speaker 2: less of an option and more of a safety net.
Speaker 2: You should just always deploy.
Speaker 1: That makes sense a way to build more robust code
Speaker 1: right from the start. Okay, let's get down to the bedrock,
Speaker 1: the core language fundamentals. Where does Matusek begin. Assuming we're
Speaker 1: coming from other language like Java or C plus plus.
Speaker 2: All, he starts with the absolute essentials. And yeah, if
Speaker 2: you're familiar with those languages, you'll find some immediate parallels
Speaker 2: for supperate comments. Okay, single line comments using and multiline
Speaker 2: comments enclosed in a selgy. Pretty standard stuff across the
Speaker 2: programming landscape.
Speaker 1: Right, no surprises there for experienced hods. What about the
Speaker 1: fundamental types of data we'll be working with in JavaScript,
Speaker 1: any quirks.
Speaker 2: Well. JavaScript has eight primitive data types. One initial thing
Speaker 2: to note, which can be a bit of a surprise,
Speaker 2: is that all numbers, whether they look like integers or decimals,
Speaker 2: are internally treated as double precision floating point numbers.
Speaker 1: Ah okay, so no true integers under the hood unless
Speaker 1: you use bigant.
Speaker 2: Later exactly, except for bigot, which is newer.
Speaker 1: Yeah.
Speaker 2: And another interesting historical tidbit, a real quirk applying the
Speaker 2: type of operator to noll actually returns the string object.
Speaker 1: Uh huh, that's weird.
Speaker 2: It is. It's a well known design flaw from the
Speaker 2: language's early days. It's inconsistent, but it's just something you
Speaker 2: have to be aware of, a historical hiccup.
Speaker 1: We just have to live with, got it. What else
Speaker 1: in the realm of data types?
Speaker 2: So beyond those basic primitives, we have user defined objects.
Speaker 2: Think of these as collections of named values or properties.
Speaker 2: You define them using curly braces with key value.
Speaker 1: Pairs, like dictionaries or maps and other languages.
Speaker 2: Pretty much. Yeah, yeah, key is the property name, value
Speaker 2: is the value. You access these values, usually with dot
Speaker 2: notation object dot property name, which is very common, right,
Speaker 2: Or you can use bracket notation object property name. That's
Speaker 2: handy when the property name is dynamic like stored in
Speaker 2: a variable, or maybe contains characters not allowed in dot notation.
Speaker 1: Okay, and then provides some built in object types for
Speaker 1: common data structures I assume exactly.
Speaker 2: Yeah, JavaScript comes equipped with several built in object types.
Speaker 2: You've got a raise for ordered lists, sets for collections
Speaker 2: of unique items, maps for key value pairs, where keys
Speaker 2: can be anything.
Speaker 1: More flexible keys than plain objects.
Speaker 2: Right. Keys can be any type in maps, And of
Speaker 2: course there are building types for dates and regular expressions too.
Speaker 2: Let's maybe focus on a few key ones first, like arrays.
Speaker 1: Sure, how do we make arrays?
Speaker 2: Usually with square brackets with comma separated values inside there's
Speaker 2: zero indexed like in many languages, and you can even
Speaker 2: nest them to create multidimensional arrays.
Speaker 1: Okay.
Speaker 2: Now there's an older array constructor, but Modissek advises against
Speaker 2: using it. It has this peculiar behavior. If you pass
Speaker 2: just a single number, oh yeah, instead of treating an
Speaker 2: array with that number in it, it creates an empty
Speaker 2: array with that specified length. So called sparse array can
Speaker 2: lead to some unexpected results down the line.
Speaker 1: Sparse arrays sounds like a potential gotcha, So what's the
Speaker 1: better way?
Speaker 2: He recommends just using the array literals for direct initialization,
Speaker 2: and also array.
Speaker 1: Dot from array dot from.
Speaker 2: Yeah, it's a static method, really powerful. You can convert
Speaker 2: iterable objects like set, strings, even maps into proper arrays.
Speaker 2: It's also a neat way to create a shallow copy
Speaker 2: of an existing array. Okay, handy, And one key takeaway
Speaker 2: about JavaScript arrays is their flexibility. They can hold a
Speaker 2: mix of different data types. You can have numbers, strings,
Speaker 2: objects all in the same array.
Speaker 1: That dynamic nature is a recurring theme with JavaScript, isn't it.
Speaker 1: What about sets? How are they useful?
Speaker 2: Sets are all about uniqueness their collections of values where
Speaker 2: each value can only appear once. Okay, and the order
Speaker 2: of elements isn't guaranteed. You create them using you set,
Speaker 2: often initializing them with an iterable like another array.
Speaker 1: In common operations.
Speaker 2: Key operations you'll use are has value to quickly check
Speaker 2: if a value exists, add value to insert a new
Speaker 2: value if it's already there, nothing happens, which is.
Speaker 1: The point, maintains uniqueness exactly.
Speaker 2: And delete value to remove a value. Delete actually returns
Speaker 2: true if the value is found and removed false otherwise.
Speaker 1: Unique unordered collections useful for things like removing duplicates quickly. Now,
Speaker 1: regular expressions always a bit tricky. What's the initial take here?
Speaker 2: Mighty Sick introduces them as patterns enclosed and forward slashes
Speaker 2: like pattern okay, and these can be followed by optional
Speaker 2: flags to modify their behavior, like g is for global
Speaker 2: matching finding all occurrences, not just the first one, and
Speaker 2: he makes the match case insensitive standard flags. Yeah. A
Speaker 2: key concept within rejecks is capturing groups. You create these
Speaker 2: by putting parts of the pattern in parentheses right to.
Speaker 1: Pull out specific parts of the match precisely.
Speaker 2: These groups are numbered from left to right, starting with one.
Speaker 2: Group zero usually represents the entire match, and these captured
Speaker 2: groups are incredibly useful. For instance, in a string's replace method,
Speaker 2: you can use one dollar, two dollars, et cetera in
Speaker 2: your replacement string to refer back to whatever those groups captured.
Speaker 1: That bag referencing is really powerful. What about common string
Speaker 1: methods that use regular expressions?
Speaker 2: Several core string methods really leverage rejects. Search rejects gives
Speaker 2: you the index of the first match, or make it
Speaker 2: a one. If no match, replace rejects replacement substitutes matches.
Speaker 2: If you use the G flag, it replaces all occurrences.
Speaker 1: Makes sense.
Speaker 2: Match read returns an array with the matches. If you
Speaker 2: use G it's an array of all matched substrings. Without
Speaker 2: G it's the first match plus any captured groups.
Speaker 1: AH different behavior.
Speaker 2: With G yep. Then there's match all pattern, which, especially
Speaker 2: with a G flag, returns an iterator of all matches.
Speaker 2: Really handy for four of flups and split regixt divides
Speaker 2: a string into an array of substrings using the rejects
Speaker 2: pattern as the delimitter. Plus there are methods directly on
Speaker 2: the rigix object itself, like exec string, which finds an
Speaker 2: next match in tracks position, and test ring, which is simpler,
Speaker 2: just returns true or false if there's a match.
Speaker 1: Okay, that gives us a solid initial grasp. Let's move
Speaker 1: on to naming things identifiers. What are the basic rules?
Speaker 2: Identifiers in the names for variables, functions, etc. Must start
Speaker 2: with a letter, an underscore, ick, or a dollar sign.
Speaker 1: No numbers at the start.
Speaker 2: Correct subsequent characters can be letters, digits, underscores, or dollar
Speaker 2: signs by convention. Variable and function names usually start lowercase
Speaker 2: and use camel case like user profile.
Speaker 1: Okay.
Speaker 2: Class names typically start uppercase pascal case like user profile,
Speaker 2: and constants are often written in all uppercase letters.
Speaker 1: Standard conventions pretty much.
Speaker 2: Of course, you can't use javascripts reserve keywords let, const, iff,
Speaker 2: et cetera as identifiers.
Speaker 1: Clear and consistent conventions are always helpful. Now, when we
Speaker 1: declare variables, JavaScript gives us let and const. What's the
Speaker 1: core difference a programmer needs to know? So?
Speaker 2: JavaScript is dynamically typed, meaning you don't declare the type,
Speaker 2: and variables can hold different types over time. You declare
Speaker 2: variables using let, you can initialize them then or assign
Speaker 2: a valulator.
Speaker 1: Okay, let is for changeable variables.
Speaker 2: Right. Cost is used to declare constants. Unlike lead. You
Speaker 2: must assign a value to a const when.
Speaker 1: You declare it, and it can't be reassigned.
Speaker 2: The binding can't. Yes, yeah, but here's a key point.
Speaker 2: If the cost variable holds an object or an array,
Speaker 2: the contents of that object or array can still be modified.
Speaker 1: Ah, So const protects the ass assignment, not the value itself.
Speaker 1: If it's mutable.
Speaker 2: Exactly, const means the binding is constant, not necessarily that
Speaker 2: the value is immutable.
Speaker 1: Got it let for reassignable variables, costs for variables intended
Speaker 1: to hold a constant reference. Now, how do we actually
Speaker 1: operate on these values? Key operators?
Speaker 2: JavaScript offers a pretty familiar set arithmetic plus kein ivelo percent,
Speaker 2: remainder and exponentiation, boolean logic andy andy and di enda
Speaker 2: nuts fame comparisons any dotic loose inequality, US strict inequality,
Speaker 2: string concatenation uses plus rocks, assignment operators plus and so on,
Speaker 2: the usual shorthand unary plus and ddea, and the ternary
Speaker 2: operator condition value false value false for concise conditionals.
Speaker 1: Okay, seems familiar. Any particular pitfalls or best practices with
Speaker 1: these operators in JavaScript?
Speaker 2: Yes, a couple of really crucial ones. First, be very
Speaker 2: cautious comparing floating point numbers for exact equality using in.
Speaker 1: Ah the classic floating point.
Speaker 2: Issue exactly due to their internal representation, things might not
Speaker 2: compare is equal when you expect them to. Matusex suggests
Speaker 2: a workaround. Convert them to strings with a fixed number
Speaker 2: of decimal places using to fixed in, and then compare
Speaker 2: the strings.
Speaker 1: Interesting workaround what's the second big one?
Speaker 2: Understanding the difference between in at and endear. This is
Speaker 2: huge in JavaScript, at least versus strict right. The loose
Speaker 2: equality attempts type coercion. It tries to convert operands of
Speaker 2: different types before comparing them. This leads to some surprising,
Speaker 2: often undesirable results like undefined null is actually.
Speaker 1: True WHOA okay.
Speaker 2: Whereas the strict equality compares both the value and the
Speaker 2: type without any type coercion, It's almost always the safer
Speaker 2: and preferred choice.
Speaker 1: So rule of thumb, use triple.
Speaker 2: Equals generally yes. Also, remember object comparison. When you compare
Speaker 2: objects including arrays and functions with eat or or, you're
Speaker 2: checking if they are the exact same object in memory
Speaker 2: now that they have the same.
Speaker 1: Contents right so VERI one would be false.
Speaker 2: Correct because there are two distinct array objects even though
Speaker 2: they look the same and related to that object. Assignment
Speaker 2: creates references. If you assign OBJA to OBJB, both variables
Speaker 2: point to the same object, modifying through OBJA effects OBGB.
Speaker 1: Those are critical distinctions, especially loose versus strict equality and
Speaker 1: object identity versus value. Now, how do we structure our
Speaker 1: code using statements.
Speaker 2: Again, if you're coming from Java or C plus plus wave,
Speaker 2: much of JavaScript's statement syntax will feel very familiar. You
Speaker 2: have standard variable assignments, expressions used for side effects like
Speaker 2: function calls, blocks of code grouped by curly braces to
Speaker 2: define scope, and the usual control flow e false for
Speaker 2: conditions while up and double loops, and the four loop
Speaker 2: for iteration. Okay, one small detail. The initialization part of
Speaker 2: a for loop in modern JavaScript typically uses lead to
Speaker 2: declare the loop, counter scoping it nicely to just the loop.
Speaker 2: Good practice, and JavaScript switch statement is maybe a bit
Speaker 2: more flexible the case. Clauses can evaluate expressions, not just
Speaker 2: constant values, so.
Speaker 1: The fundamental control flow is quite similar. What about statements
Speaker 1: that are more unique to JavaScript or have specific nuances.
Speaker 2: There are a few that stand out. Four of specifically
Speaker 2: designed for iterating over the values of iterable.
Speaker 1: Objects, like a raise sets strings.
Speaker 2: See exactly A ray sets map strings. Plain user defined
Speaker 2: objects aren't itterable by default, that you can make them miserable.
Speaker 1: Okay, And four in fian iterates over.
Speaker 2: The property names or keys of an object. Yeah, you
Speaker 2: can use it with user defined objects. A raise where
Speaker 2: it iterates index names as strings. Even strings iterating indices,
Speaker 2: but be aware it iterates over inherited innumerable properties too,
Speaker 2: and it might skip missing elements and sparse arrays. So
Speaker 2: it has its uses, But Forurian is often preferred for
Speaker 2: iterating values in collections.
Speaker 1: Gotcha, what else?
Speaker 2: The throw statement lets you intentionally raise an exception. Interestingly,
Speaker 2: in JavaScript you can throw a value of any type,
Speaker 2: not just specific.
Speaker 1: Air object, really any type.
Speaker 2: Yep, And there isn't a strict distinction like checked versus
Speaker 2: unchecked exceptions found in some other languages.
Speaker 1: And how do we handle these thrown values, these exceptions.
Speaker 2: That's where the tricatch finally block comes in code that
Speaker 2: my throw goes in the try block. Standard If an
Speaker 2: exception happens, control jumps to the catch block. You can
Speaker 2: have an optional variable in catch to hold the throne value. Okay,
Speaker 2: and the finally block, if you include it, always executes
Speaker 2: after trying cash whether an exception occurred or not. Great
Speaker 2: for cleanup makes sense. An interesting quirk If try or
Speaker 2: catch has a return, break or continue, its execution is
Speaker 2: sort of paused until the finally block finishes.
Speaker 1: Oh, okay, finally really means finally pretty much.
Speaker 2: JavaScript also has labeled statements label name that statement. They're
Speaker 2: mainly useful with break and continue inside nest of loops
Speaker 2: or switch statements. Break label name exits the specific label
Speaker 2: loop or switch continue label name jumps to the next
Speaker 2: iteration of the labeled loop.
Speaker 1: Allows for more fine grained control in nested structures.
Speaker 2: Exactly and Finally, the return statement sends a value back
Speaker 2: from a function. If there's no return, or just return,
Speaker 2: the function implicitly returns undefined functions mainly used for side
Speaker 2: effects are sometimes called procedures.
Speaker 1: That's a good overview of JavaScript's control flow. Let's move
Speaker 1: on to functions. A cornerstone.
Speaker 2: Absolutely the most common way to define what is function?
Speaker 2: Function name, param one, PERM.
Speaker 1: Two standard syntax.
Speaker 2: When working in HTMOL, it's generally good practice to define
Speaker 2: functions in script tags inside the head. This ensures they're
Speaker 2: defined before any code in the body tries to call them.
Speaker 1: Makes sense.
Speaker 2: Functions can be recursive call themselves. They can be nested
Speaker 2: inside other functions. Variables declared inside, including parameters, have local scope,
Speaker 2: but functions can access variables from their outer environment up
Speaker 2: to the global scope unless shadowed.
Speaker 1: Locally standard lexical scoping right.
Speaker 2: One key concept to knowe is.
Speaker 1: Hoisting ah hoisting.
Speaker 2: Function declarations and variables declared with var the older way
Speaker 2: are conception moved to the top of their scope during compilation.
Speaker 1: So you can sometimes call a function before its definition appears.
Speaker 2: In the code. Technically yes, but it's generally much better
Speaker 2: practice to define functions before you use them, just for
Speaker 2: clarity and predictability.
Speaker 1: Hoisting another one of JavaScript's interesting behaviors to keep in mind. Now,
Speaker 1: testing is crucial. Does Matischik's touch on that.
Speaker 2: He does include a brief introduction. He mentions using the
Speaker 2: Mocha testing framework and the Chai assertion.
Speaker 1: Library common tools yeah for.
Speaker 2: Writing and running tests, often within a browser. For client
Speaker 2: side code. He outlines the basic structure describe blocks to
Speaker 2: group tests, it blocks for individual test cases with descriptive
Speaker 2: names inside it. Use assertions from Chi's assert object to
Speaker 2: check if your code behaves as expected. He shows examples
Speaker 2: like assert dot is true, assert dot is false, assert
Speaker 2: dot equal for loose equality.
Speaker 1: AH, loose again. Is there a strict one?
Speaker 2: Yes, assert dot strict equal and not equal not strict equal.
Speaker 2: He also mentions assert dot org approximately for comparing floats
Speaker 2: within a tolerance.
Speaker 1: Good for those floating point comparisons we talked about exactly.
Speaker 2: He briefly covers setting up Mocha and Chai in an
Speaker 2: HTML page, maybe using CD in links, and initializing Mocha
Speaker 2: to run the tests.
Speaker 1: A quick taste of the testing landscape. Good to know
Speaker 1: it's covered. Now the book moves into JavaScript in more detail.
Speaker 1: What key enhancements and deeper concepts does it explore there?
Speaker 2: Right? This section builds on the basics getting nuance in
Speaker 2: introducing more advanced features. It starts with destructuring.
Speaker 1: Destructuring I like the sound of that.
Speaker 2: It's really elegant. A concise way to extract values from
Speaker 2: objects and arrays and assign them directly to variables you
Speaker 2: use for objects and for arrays on the left side of.
Speaker 1: An assignment, so you can pull out just the pieces
Speaker 1: you need exactly.
Speaker 2: You can pull out specific properties or elements. You can
Speaker 2: even rename properties during extraction, like let username nice, and
Speaker 2: you can provide default values if a property might be
Speaker 2: missing nice. It's especially powerful in function parameter lists. You
Speaker 2: can destructure an object passed as an argument right in
Speaker 2: the parameter definition.
Speaker 1: Destructuring sounds like a great tool for cleaner, more readable code.
Speaker 1: What about revisiting data types? With a more in depth
Speaker 1: look any more nuances.
Speaker 2: Yes, numbers again reiterated. They're mostly sixty four bit i
Speaker 2: ee seven hundred and fifty four floats except for bigot.
Speaker 2: He mentions the special values infinity, infinity, and nan not
Speaker 2: a number right nan, and the is finite function to
Speaker 2: check for actual finite numbers. Also useful constants like number
Speaker 2: dot mn value, number dot x value and number dot
Speaker 2: epsilon that tiny difference.
Speaker 1: Value okay, strings.
Speaker 2: Key point is immutability. Once created, you can't change individual characters.
Speaker 2: You can access characters by index read only. He details
Speaker 2: escape characters like n and unicode escapes.
Speaker 1: Too right, and symbols you mentioned those briefly.
Speaker 2: Symbols are unique, immutable primitive values oh created with symbol
Speaker 2: even symbol desks create two different.
Speaker 1: Symbols guaranteed uniqueness. What are they used for?
Speaker 2: Often used as unique property keys on odds. Maybe to
Speaker 2: add metadata or behavior without risking name collisions with other
Speaker 2: properties or future language editions.
Speaker 1: Clever. What about advanced array and set operations for arrays?
Speaker 2: He mentions unshift and shift for adding removing from the beginning,
Speaker 2: but notes they can be less efficient than push pop.
Speaker 2: At the end, he also highlights Han's own property. It's
Speaker 2: a reliable way to check if an object, including an
Speaker 2: array actually has a property directly on itself, not inherited,
Speaker 2: and useful for distinguishing real elements from undefined slots in
Speaker 2: sparse arrays. Such JavaScript doesn't have built in methods for
Speaker 2: standard set operations like union, intersection, difference. Oh really yeah,
Speaker 2: but metwusex shows how you can implement them yourself, using
Speaker 2: the spread syntax to convert sets to arrays and then
Speaker 2: using array methods like filter along with the sets as method.
Speaker 1: So a bit of manual work for those. What about
Speaker 1: maps and weak maps? How do they differ?
Speaker 2: Maps are key value collections where keys can be any
Speaker 2: data type, objects, function primitives. Key equality is based on identity.
Speaker 1: Okay.
Speaker 2: He cautions that if you use object literals as keys
Speaker 2: at one and ad on one are different keys because
Speaker 2: they're different objects in memory, you need to use the
Speaker 2: same object instance right.
Speaker 1: Identity matters.
Speaker 2: Week maps week maps are specialized. Keys must be objects
Speaker 2: and they're held.
Speaker 1: Weekly weekly meaning.
Speaker 2: Meaning if the object used as a key is no
Speaker 2: longer referenced anywhere else, it can be garbage collected and
Speaker 2: the entry automatically disappears from the weak.
Speaker 1: Map ah for memory management.
Speaker 2: Exactly because of this week, maps aren't iterable and have
Speaker 2: limited methods get said has delete. Their state can be
Speaker 2: nondeterministic due to garbage collection timing.
Speaker 1: Niche but potentially powerful. Let's move to promises fundamental for
Speaker 1: async JavaScript.
Speaker 2: Yes, promises handle results of asynchronous operations like network requests.
Speaker 2: You create one with new promise function resolve, reject.
Speaker 1: The executor function right it.
Speaker 2: Gets resolved, and reject functions You call resolvevol with the
Speaker 2: result on success, reject with an error on failure. Promises
Speaker 2: capture their surrounding environment. When created. You handle the results
Speaker 2: using then unfulfilled, unrejected or then unfulfilled catch unrejected.
Speaker 1: Chaining the dot chain is key very much.
Speaker 2: So it's how you sequence asynchronous actions.
Speaker 1: Okay, what about the finer points of type conversions coercion.
Speaker 2: JavaScript does a lot of automatic conversion coercion. You can
Speaker 2: also do explicit conversions using number straing, boolean big, and
Speaker 2: parson pars float. He warns against using new with number
Speaker 2: string or boolean That creates wrapper objects not primitives, which
Speaker 2: can cause confusion.
Speaker 1: Good tip.
Speaker 2: All objects have a toe string method. Good practice to
Speaker 2: override it. For custom objects, parsint and parse float try
Speaker 2: to parse numbers from the start of a string, stopping
Speaker 2: at the first non numeric character, or non numeric after
Speaker 2: a decimal.
Speaker 1: For pars float, good to know how they handle non
Speaker 1: numeric parts. The book lists keywords too. Any key advice
Speaker 1: there besides.
Speaker 2: The obvious don't use keywords as names. He suggests avoiding
Speaker 2: older reserved words, even if not strictly enforced. Now built
Speaker 2: in object property method names, htmail, element attribute names and
Speaker 2: event handler names basically choose descriptive names that won't clash.
Speaker 1: Sound advice. Now you mentioned good and bad operators earlier,
Speaker 1: can you elaborate?
Speaker 2: He discusses operator precedence, order of operations, and associativity for
Speaker 2: operators with same precedence. There's a table outlining this. For
Speaker 2: key operators, he highlights logical and A and R as
Speaker 2: short circuiting.
Speaker 1: Meaning they don't always evaluate the second part exactly.
Speaker 2: And aaran stops if the left side is falsey yeah
Speaker 2: stops if the left side is truthy. They often return
Speaker 2: the value of the operand that determine the result not
Speaker 2: necessarily true orful right.
Speaker 1: The Y five default value trick yep.
Speaker 2: Then there's the nullish coalescing operator. Yeah. It returns the
Speaker 2: right operad only if the left one is null or undefined.
Speaker 2: Otherwise it returns the left operand.
Speaker 1: So it's stripter than which triggers on any falsey correct.
Speaker 2: He stresses using parentheses when mixing with milan or due
Speaker 2: to precedence rules. As for bad operators, he references Crockford's
Speaker 2: JavaScript The good parts. For instance, the prefixed postfix increment,
Speaker 2: plus plus and decrement operators are sometimes discouraged. Why is
Speaker 2: that they can make code less clear, especially when used
Speaker 2: inside complex expressions. Using plus one or nakeld one is
Speaker 2: often more explicit and less aero prone.
Speaker 1: Readability and avoiding subtle bugs good principles. Let's revisit functions
Speaker 1: more details in this section.
Speaker 2: Definitely several ways to define them. The standard function declaration
Speaker 2: function expressions. Assigning function to a variable can be anonymous
Speaker 2: or named. The function constructor takes code as strings. Generally
Speaker 2: bad idea right, avoid that one and erow functions which
Speaker 2: have concise syntax and crucially lexical this binding.
Speaker 1: Welcome back to this right.
Speaker 2: All functions have a name property. JS tries to infer
Speaker 2: it parameter versus argument distinction parameters and definition arguments in
Speaker 2: the call JS doesn't enforce matching counts. Extra ARGs ignored
Speaker 2: missing ones are undefined.
Speaker 1: Flexible, but potentially error prone if you're not careful.
Speaker 2: True. The older arguments object array like list of all
Speaker 2: orgs and traditional functions is mentioned, but rest parameters dot
Speaker 2: org are generally preferred.
Speaker 1: Now okay.
Speaker 2: Key concept functions are first class data. Assign them to variables,
Speaker 2: put them in a raise, pass them as arguments callbacks.
Speaker 2: A function's toastring returns its source code. Its length property
Speaker 2: is the number of declared parameters excluding rest.
Speaker 1: Functions as values is super powerful it is He revisits
Speaker 1: recursion with a factorial example.
Speaker 2: You can add properties directly to a function object itself,
Speaker 2: like myfunk dot counter equals zero as an alternative to
Speaker 2: globals sometimes and he briefly mentions dot call, dot ply
Speaker 2: and dot bind for controlling this value during invocation.
Speaker 1: Right controlling execution context. Now generators function what's the deeper doug.
Speaker 2: Generators are special functions that can pause and resume. Defined
Speaker 2: with function calling one doesn't run it, but returns a
Speaker 2: generator object, which is an iterator inside the yield keyword
Speaker 2: returns a value and pauses execution. Calling next on the
Speaker 2: generator object resumes it until the next yield or the end,
Speaker 2: and next returns an object like the yielded value done false.
Speaker 2: When the generator finishes, reaches an end or hits a return,
Speaker 2: next returns value final value or undefined done through. Once done,
Speaker 2: it's done, can't restart it, Nope. They're great for creating
Speaker 2: custom iterators easily. He shows a simple half end generator example.
Speaker 1: Generators sound useful for sequences and that ties into iterators
Speaker 1: and iterables exactly.
Speaker 2: An object is iterable if it implements the iterable protocol.
Speaker 2: That means having a method keyed by the special symbol
Speaker 2: symbol dot iterator. This method must return an iterator object
Speaker 2: which has a next method. Often the easiest way to
Speaker 2: implement symble dot iterator is just to make it a
Speaker 2: generator function. Mitisek shows an example making an object with start,
Speaker 2: step and iterable using a generator.
Speaker 1: So that's the magic behind how four off works on
Speaker 1: different things. Finally, let's really get into the details of
Speaker 1: objects themselves.
Speaker 2: Right, objects are fundamental collections of key value pairs. Create
Speaker 2: them with literals key dot value meat keyser useles, strings
Speaker 2: or symbols, access with dot, a bracket and notation.
Speaker 1: We covered the shorthand.
Speaker 2: Yeah. If you have a variable let make toyota and
Speaker 2: want an object make toyota, you just write that make
Speaker 2: nice shortcut cool. Checking for properties, the in operator checks
Speaker 2: if a property exists, including inherited ones. Fore end loops
Speaker 2: over innumerable property names including inherited okay. Creating objects literals,
Speaker 2: object adding properties dynamically, constructor functions with new using this
Speaker 2: inside yeah and object dot create prototype, which creates a
Speaker 2: new object with a specific prototype you provide.
Speaker 1: And copying objects still just.
Speaker 2: References, still just references. Assignment copies the reference, not the object.
Speaker 2: Modifying one effects the other if they point to the
Speaker 2: same object. Methods are just functions that are are properties
Speaker 2: of an object. Concise syntax and literals.
Speaker 1: My method, got it now? This keyword always a fun
Speaker 1: one has it explained here.
Speaker 2: Its value is determined by how a function is called,
Speaker 2: the call site evaluated at run time. Inside a method
Speaker 2: called like UBJ dot method, this is usually object. In
Speaker 2: a constructor called with new, this is the new object
Speaker 2: being created. Makes sense in a regular function called directly,
Speaker 2: not as a method in non strict mode, this is
Speaker 2: the global object window and browsers, but in strict mode
Speaker 2: it's undefined.
Speaker 1: AH. Strict mode changes things again.
Speaker 2: Yes, and a function inside another function. This inside the
Speaker 2: inner one follows the regular function rules. It doesn't automatically
Speaker 2: inherit the outer this unless unless it's an erowfunction. Erofunctions
Speaker 2: capture this value from their surrounding lexical scope. They don't
Speaker 2: have their own this binding.
Speaker 1: That's a key difference for EROW functions.
Speaker 2: Event handlers femail event handlers. This usually refers to the
Speaker 2: htmail element that triggered.
Speaker 1: The events, so context is everything for this. You've mentioned
Speaker 1: prototypes a lot. Let's nail that down.
Speaker 2: Every JavaScript object has an internal link to another object,
Speaker 2: its prototype. You can get it with object dot get prototype.
Speaker 2: When you access a property, If the object doesn't have
Speaker 2: it directly, JavaScript looks at its prototype. If it's not there,
Speaker 2: it looks at the prototypes prototype, and so on up
Speaker 2: the chain.
Speaker 1: The prototype chain exactly.
Speaker 2: Until it finds the property or hits the end where
Speaker 2: the prototype is null. Object dot prototype is the base
Speaker 2: for most objects. Setting a property always happens directly on
Speaker 2: the object, never modifies the prototype chain directly like.
Speaker 1: That and properties have hidden attributes descriptors Yes, properties.
Speaker 2: Have attributes like innumerable, does it show and foreign writeable?
Speaker 2: Can its value be changed? And configurable? Can it be
Speaker 2: deleted or its attributes changed? You can control these with
Speaker 2: object dot defined property.
Speaker 1: Fine grained control. Now, how do classes fit in with prototypes?
Speaker 2: Classes from e S twenty fifteen are mostly syntactic sugar
Speaker 2: over the existing prototype based inheritance. They provide a clear
Speaker 2: or more familiar syntax from many programmers, a blueprint kind
Speaker 2: of my class constructor. Defining a class essentially creates a
Speaker 2: constructor function and adds methods to its prototype property new
Speaker 2: my class calls the constructor this inside refers to the instance,
Speaker 2: and inheritance uses the extends keyword. Class subclass extends superclass.
Speaker 2: The subclass prototype is linked to the superclass prototype inheriting methods.
Speaker 2: You can override methods if no extends it implicitly extends object.
Speaker 1: So classes organize the prototype stuff. Can we still mess
Speaker 1: with prototypes directly with classes?
Speaker 2: Yes, The my class dot prototype object holds the method
Speaker 2: definition shared by all instances. You can still add methods
Speaker 2: directly to my class dot prototype after the class definition
Speaker 2: and all instances will get it. Object prototype of instance
Speaker 2: still works. Object I creates still works. The underlying mechanism.
Speaker 1: Is prototypes that clarifies the class prototype relationship. Now JavaScript evolves.
Speaker 1: How do we handle older browsers that don't support new features?
Speaker 2: Two main tools, transpilers and polyfills. Transpilers like Babble convert
Speaker 2: newer syntax hegany aerofunctions classes into older compatible syntax. Polyfills
Speaker 2: are pieces of code that provide implementations for features missing
Speaker 2: in older environments, like if a browser doesn't have the
Speaker 2: raate oup prototype dot includes method, you can include a
Speaker 2: polyfil that adds it.
Speaker 1: So transpilers handle syntax. Polyphils handle missing functions objects exactly.
Speaker 2: Services like polyfil that io can even serve only the
Speaker 2: polyfills needed by the specific browser making the request, but
Speaker 2: you need to be mindful of download size.
Speaker 1: Essential tools for cross browser compatibility. Last language topic before
Speaker 1: the DOM.
Speaker 2: Json json JavaScript object notation lightweight text format for data exchange,
Speaker 2: very common.
Speaker 1: How do we use it in JS?
Speaker 2: Built in methods? Jsonstring ifi object converts a JS object
Speaker 2: value into a Jason string. Json dot parse jsonstring converts
Speaker 2: a jsonstring and do a JAS object value.
Speaker 1: Simple enough any limitations.
Speaker 2: Yes, Functions, symbols undefined are generally lost or become null
Speaker 2: During stringification, dates become ISO format strings, infinity and nan
Speaker 2: become null. Non innumerable properties and symbol keys are ignored, so.
Speaker 1: It's mainly for plain data.
Speaker 2: Structures pretty much. You can customize serialization by defining it
Speaker 2: low chasm method on an object JSON dot string offy
Speaker 2: will call that if it exists.
Speaker 1: Good to know. Okay, let's shift gears to client side
Speaker 1: JavaScript and the DOM. This is where it gets visual exactly.
Speaker 2: The rest of the book focuses on guys and the
Speaker 2: browser and using the DOM to interact with the page.
Speaker 2: It starts with some essential HTML review right the structure
Speaker 2: HML page is a text file with tags container tags,
Speaker 2: tag content tag, empty tags like BR basic structure doctri
Speaker 2: type HDL HTML head with title body. Tags can have
Speaker 2: attributes name value like AID HTML tags attributes are case
Speaker 2: in sensitive, but JS is case sensitive, CSS handles is
Speaker 2: styling and.
Speaker 1: How do we connect our jawas script to the HTML.
Speaker 2: A few ways embedcode directly in script tags in header body, Yeah,
Speaker 2: link to external JS files using script as rc URLJS
Speaker 2: script usually in head if you use src code inside
Speaker 2: the tags is ignored.
Speaker 1: External files are generally better for organization.
Speaker 2: Yes, especially for larger scripts. You can also use evan
Speaker 2: handler attributes like on click JS code directly on HTML elements,
Speaker 2: though separating JS is often cleaner. Function definitions best in head,
Speaker 2: scripts and body execute as the page loads. NoScript provides
Speaker 2: fallback content if JS is off.
Speaker 1: Okay, Now, the dom itself a tree of nodes.
Speaker 2: Think of it as a live interactive map or tree,
Speaker 2: representing everything on the page. Elements, attributes, text. JavaScript can
Speaker 2: read and change this tree. Any changes JavaScript makes to
Speaker 2: the damber reflected immediately in the browser window. That's the
Speaker 2: core of dynamic web.
Speaker 1: Pages, a live tree we can modify. Let's start building
Speaker 1: things widgets and events. Buttons.
Speaker 2: The two skip covers buttons. First two ways input type,
Speaker 2: button value click me or button click me button. The
Speaker 2: button tag is newer, more flexible, can contain images, et cetera.
Speaker 2: Requires a closing tag. JS can change button text value
Speaker 2: for input inner HTML for button.
Speaker 1: How do we find these buttons in our code?
Speaker 2: Need to find the widgets document dot G element B
Speaker 2: I E E finds the single element with a unique ID.
Speaker 2: Document dot G elements be by tag name. Tagname gets
Speaker 2: a live collection of all elements with that tag.
Speaker 1: Get element by i'd for specifics, get elements by tag
Speaker 1: name for groups text fields for user input use.
Speaker 2: Input type text can set size for a visible width
Speaker 2: value for initial text. To get user input, find the
Speaker 2: element again by ID and read its dot value property
Speaker 2: in JavaScript simple enough? How do HTML forms fit in
Speaker 2: form acts as a container for related inputs, usually for
Speaker 2: submitting data. Submit buttons type submit, trigger, submission, reset buttons
Speaker 2: type reset clear the form plain buttons type button do
Speaker 2: nothing by default. A button inside a form default to
Speaker 2: type submit if unspecified. Okay forms define a scope for
Speaker 2: the name attribute on inputs. This name identifies the data
Speaker 2: when submitted. I must be unique on the whole page.
Speaker 2: Forms can't be nested. Pressing it entering an input field
Speaker 2: often submits the form if there's a submit put.
Speaker 1: Forms group inputs for submission. How about validation? Making sure
Speaker 1: input is.
Speaker 2: Okay HTAM all five added built in validation attributes required,
Speaker 2: makes a field mandatory, pattern rejects checks input against a
Speaker 2: regular expression. Placeholder text gives a hint, and.
Speaker 1: Built in checks are nice.
Speaker 2: Custom validation use the unsubmitted vent handler on the form tag,
Speaker 2: set it to return my function. If my function returns false,
Speaker 2: submission is canceled. Inside the function. You can use event
Speaker 2: dot prevent to fall two.
Speaker 1: Client side validation gives quick feedback what happens on successful submission.
Speaker 2: The action you URL attribute on the form says where
Speaker 2: to send data, method says how Usually get or post.
Speaker 2: Get appens data to URL, post sends it in the
Speaker 2: request body.
Speaker 1: Okay, any other useful text widgets.
Speaker 2: Input type email, checks for at, input type, numbers, spinners,
Speaker 2: input type earl, basic, url, check textteria for multiline input
Speaker 2: daytime inputs exist, but support varies.
Speaker 1: Good range. What about non text inputs, radio, buttons, checkboxes.
Speaker 2: Input type radio used in groups with the same name.
Speaker 2: Selecting one d selects others in the group. Input type
Speaker 2: checkdocs are independent selections others. Input type image src images,
Speaker 2: submit button, input type color colorpicker, input type hidden data
Speaker 2: smitted but not visible, input type range slider.
Speaker 1: Lots of input types. Now how do these react to users? Events?
Speaker 2: Events are actions user clicks, keypresses, pageloads handled by attributes
Speaker 2: like on click JS code. Event names are a lowercase
Speaker 2: in HTML attributes on click often CamelCase and JS on
Speaker 2: click common events dot onload onload for bodyframes, mouse dot on,
Speaker 2: click on, be able to click on mouse down on
Speaker 2: mouse up on mouseover on mouse out on mass move,
Speaker 2: pointer events on pointer out, unify, mouse touch, focus, dot on,
Speaker 2: focus on, blur, change on, change on select form, dot on,
Speaker 2: reset on submit return false, camp image, dot on a
Speaker 2: board on error, keyboard dot donkey down on keypress, event
Speaker 2: dot key on KIAP.
Speaker 1: That's a lot of events. What's in the event object?
Speaker 2: The event object pass to Handlers have info like event
Speaker 2: dot type ag click, and event dot target the element.
Speaker 1: That triggered the A M bubbling. What's that?
Speaker 2: When an event happens on an element, it bubbles up
Speaker 2: the DOM tree. First the target handles it, then its parent,
Speaker 2: then its parent's parent, all the way up.
Speaker 1: So a click on a button also clicks the div
Speaker 1: it's inside and the body potentially yes.
Speaker 2: Each ancestor gives a chance to handle the event unless
Speaker 2: a handler stops propagation. It's useful for event delegation, handling
Speaker 2: events for many children by listening on a parent efficient.
Speaker 1: Okay, let's dive deeper into using the dom manipulating that
Speaker 1: tree right.
Speaker 2: Starts with a window object. It's the global object. In browsers,
Speaker 2: document is actually a property of window.
Speaker 1: So window, dot, document and document are the same.
Speaker 2: Usually yes, because window is the global scope, window represents
Speaker 2: the browser. Window itself has properties like location, kurt url
Speaker 2: can change it to navigate history, back, forward, navigateator, browser info.
Speaker 1: What about methods on window.
Speaker 2: User interaction, dot alert, proft, confirmed timers, dot delay runs
Speaker 2: funk once after delay milliseconds, set interval, fagigible runs funk
Speaker 2: repeatedly every interval milliseconds. Both return IDs to use with
Speaker 2: clear timeout or clear interval to stop them. My two
Speaker 2: sex shows using set timeout with window dot location for
Speaker 2: a time to redirect.
Speaker 1: Timers are key for dynamic stuff. What about finding nodes
Speaker 1: Beyond the basics, we.
Speaker 2: Have document dot body the body element, document the document
Speaker 2: element to the HTML element. More finding methods. Document dot
Speaker 2: elements by class name gets elements by class. Document dot
Speaker 2: query selector gets the first element matching a CSS selector.
Speaker 1: H ah, CSS selectors powerful very.
Speaker 2: And document dot query selectoral selector gets all elements matching
Speaker 2: the CSS selector, returning a static notalist. Much more flexible.
Speaker 1: Targeting so we can find things precisely. How do we
Speaker 1: create and add new things to the dawn.
Speaker 2: Document dot create element tag name creates a new element node,
Speaker 2: set its tech content with no dot text content equals text.
Speaker 2: Add attributes with element dot set attribute name value.
Speaker 1: Okay, create the node, How to put it on the page.
Speaker 2: Use methods on the parentode where you want to add it.
Speaker 2: Parentode dot penchild child node adds it at the end.
Speaker 2: Parentnode dot insert before new nodes. Existing node inserts before
Speaker 2: another child parentnode dot remove child noode removes it parentode
Speaker 2: dot replaced child new noode. Old nodes swaps one for another.
Speaker 1: Standard premanipulation copynotes.
Speaker 2: No dot clone node deep. If deep is true, it
Speaker 2: copies the node and everything inside it. If false, just
Speaker 2: the node itself got it.
Speaker 1: What about properties and methods specific to element objects.
Speaker 2: Elements have element dot tag name oopcase element dot inner
Speaker 2: HTML get sets the HTML content inside the element element
Speaker 2: dot or HTML get sets the elements full HTML, including
Speaker 2: its own tags. Element dot attributes is a collection of
Speaker 2: attribute nodes. Element dot class name is the string of classes.
Speaker 2: Element dot class list is better a list object with
Speaker 2: ad remove toggle contains methods for classes. Element dot style
Speaker 2: accesses inline styles.
Speaker 1: Classless sounds much easier for managing classes elements specific methods.
Speaker 2: They have their own get elements by class name, querity
Speaker 2: selector query selectoral that search only within that element's descendants.
Speaker 2: Also element dot, get attribute, element dot or room attribute,
Speaker 2: and element dot insert adjacent HTML where htmail inserts HTML
Speaker 2: strings relative to the element before begin after begin before whatever.
Speaker 1: Insert adjacent HTML seems handy for adding chunks of HTML.
Speaker 1: What about text nos character data.
Speaker 2: Textnodes represent the actual text content. They have properties like data,
Speaker 2: the text, and length. They have methods like a pen
Speaker 2: data delete, data, replaced, data, and removed to manipulate or
Speaker 2: remove the text.
Speaker 1: Okay, the show tree example. What does that illustrate?
Speaker 2: It's a practical demo. Usually a button click triggers JS
Speaker 2: that recursively traverses the dom tree from document dot body down.
Speaker 2: It logs info about each node name, attributes content to
Speaker 2: the console. It really helps visualize that tree structure and
Speaker 2: how JS can walk through it.
Speaker 1: Seeing that tree logged out makes the dom much more concrete.
Speaker 1: It sounds like, as the book's afterward notes, this is
Speaker 1: a strong foundation for just a starting point.
Speaker 2: Absolutely my t sake. It's clear it's not exhaustive, it's
Speaker 2: an entry point for much more learning in the vast
Speaker 2: world of JavaScript and webdev.
Speaker 1: Well that brings us towards the end of this deep dive.
Speaker 1: My key takeaway from quick JavaScript is its effectiveness for
Speaker 1: experienced programmers needing a fast, targeted intro to JS and
Speaker 1: the DOM. But you absolutely have to understand its scope,
Speaker 1: who it's for, and what it deliberately leaves out.
Speaker 2: Yeah, and it's fascinating reflecting on some of those Jamas
Speaker 2: specific things we hit on, like it being the only
Speaker 2: native browser language that type of null oddity, and the
Speaker 2: whole prototype system underpinning objects, and even the newer class syntax.
Speaker 1: And for you, our listener, we hope this dive gave
Speaker 1: you that quick yet thorough understanding you needed, hitting the
Speaker 1: essentials without getting bogged down in exhaustive detail.
Speaker 2: We definitely encourage you now to explore the areas that
Speaker 2: sparked your interest. Was it promise and async? Yeah, dug
Speaker 2: deeper there, dom manipulation for interactivity, start building things robust code,
Speaker 2: maybe look more into testing with Mocha and Chai.
Speaker 1: And a final thought to leave you with, think about
Speaker 1: JavaScript's journey. A language often described as being maybe hastily
Speaker 1: put together initially has become this absolute powerhouse driving modern
Speaker 1: web experiences. What does that evolution tell us about the
Speaker 1: balance between say, initial design perfection versus continuous adaptation and
Speaker 1: community driven growth and technology Something to ponder. Thanks for
Speaker 1: joining us on this deep dive.