WEBVTT 1 00:00:00.080 --> 00:00:02.520 So if you tell your web browser to subtract the 2 00:00:02.640 --> 00:00:06.240 number one from the word five like text that actually 3 00:00:06.320 --> 00:00:09.039 spells out the number five, it somehow gives you the 4 00:00:09.119 --> 00:00:09.759 number four. 5 00:00:09.759 --> 00:00:13.279 Right, which logically makes absolutely no sense, none at all. 6 00:00:13.480 --> 00:00:15.599 But wait, if you tell it to add the number 7 00:00:15.640 --> 00:00:18.480 one to the text five, it suddenly gives you fifty one. 8 00:00:18.640 --> 00:00:21.760 Yeah, it just glues them together. It's wild, It really is. 9 00:00:22.399 --> 00:00:25.879 So. Welcome to the deep dive today. Our mission is 10 00:00:25.920 --> 00:00:28.920 to basically decode what on earth is happening behind the 11 00:00:28.920 --> 00:00:31.600 glass of your screens. You know, we really want to 12 00:00:31.600 --> 00:00:37.240 demystify this incredibly powerful, but honestly slightly alien world of 13 00:00:37.320 --> 00:00:38.240 computer programming. 14 00:00:38.280 --> 00:00:40.320 And it is alien. I mean, we are surrounded by 15 00:00:40.320 --> 00:00:43.119 these machines constantly, right, We're carrying them in our pockets, 16 00:00:43.159 --> 00:00:46.560 We're wearing them on our wrisks, yeah, everywhere exactly. Yet 17 00:00:46.600 --> 00:00:49.280 for most people, the actual mechanism of how we talk 18 00:00:49.320 --> 00:00:52.840 to them, it re means completely opaque. We just tap 19 00:00:52.880 --> 00:00:55.320 a colorful little icon and just, you know, hope the 20 00:00:55.359 --> 00:00:56.399 machine understands our. 21 00:00:56.320 --> 00:00:59.280 Intent, which is exactly why we are diving into some 22 00:00:59.320 --> 00:01:03.399 excerpts from truly fascinating source today. We're looking at the 23 00:01:03.439 --> 00:01:08.079 acclaimed book Eloquent JavaScript second edition by Marine Haverbak. 24 00:01:08.200 --> 00:01:09.040 It's a great choice. 25 00:01:09.120 --> 00:01:11.680 Yeah, it is, because what makes this material really stand 26 00:01:11.719 --> 00:01:14.319 out is that it's not it's not just some dry 27 00:01:14.519 --> 00:01:17.280 technical manual about like writing web code. 28 00:01:17.359 --> 00:01:18.040 No, not at all. 29 00:01:18.079 --> 00:01:21.640 It reads much more like a well, a philosophical exploration. 30 00:01:21.799 --> 00:01:22.079 Really. 31 00:01:22.359 --> 00:01:25.640 It looks at how we bridge this massive communication gap 32 00:01:25.680 --> 00:01:30.439 between us, you know, squishy biological organisms who excel at 33 00:01:30.480 --> 00:01:35.159 social and spatial reasoning and these completely unfeeling manipulators of 34 00:01:35.239 --> 00:01:36.159 meaningless data. 35 00:01:36.359 --> 00:01:39.439 Yeah, the author frames that disconnect so perfectly. I mean, 36 00:01:39.560 --> 00:01:42.599 think about human intelligence for a second. Okay, we constantly 37 00:01:42.640 --> 00:01:46.840 rely on context, nuance, social cues just to understand each other. 38 00:01:47.120 --> 00:01:50.159 Computers have absolutely none of that, zero, right, They don't 39 00:01:50.159 --> 00:01:53.079 inherently understand the concept of like a photo or a 40 00:01:53.120 --> 00:01:56.439 bank account. They just shuffle data around based on these 41 00:01:56.599 --> 00:01:58.920 incredibly rigid, unthinking rules. 42 00:01:59.239 --> 00:02:02.000 So we have to basically build a bridge to interact 43 00:02:02.040 --> 00:02:04.239 with them. And looking at the history of it all, 44 00:02:04.280 --> 00:02:06.319 we kind of settled on two different approaches. 45 00:02:06.439 --> 00:02:07.599 Yeah, that's a good way to put it. 46 00:02:07.640 --> 00:02:11.120 The first approach, it relies heavily on our human talent 47 00:02:11.199 --> 00:02:15.560 for spatial reasoning, like we build graphical interfaces. We literally 48 00:02:15.639 --> 00:02:18.080 draw a little folders on the screen. We swipe, we 49 00:02:18.199 --> 00:02:21.599 pin exactly, we drag and drop things into a virtual 50 00:02:21.639 --> 00:02:22.199 trash can. 51 00:02:22.599 --> 00:02:25.159 And I mean it makes perfect sense why that approach 52 00:02:25.240 --> 00:02:28.759 won the mainstream, right. It makes the computer feel approachable, 53 00:02:29.000 --> 00:02:30.319 almost physical in a way. 54 00:02:30.439 --> 00:02:30.680 Right. 55 00:02:31.319 --> 00:02:34.479 But there is a hidden cost to all that convenience, 56 00:02:34.840 --> 00:02:37.319 because when you rely entirely on a point and click 57 00:02:37.400 --> 00:02:41.680 graphical interface, your power is strictly limited to the imagination 58 00:02:41.759 --> 00:02:43.319 of the person who designed that interface. 59 00:02:43.400 --> 00:02:44.479 Oh that's a really good point. 60 00:02:44.599 --> 00:02:46.800 Yeah. You can only click the specific buttons they decided 61 00:02:46.800 --> 00:02:49.319 to draw for you, you know, and only in the 62 00:02:49.360 --> 00:02:51.039 exact ways they allow you to click them. 63 00:02:51.199 --> 00:02:54.199 Let's ground this in like a real world scenario for 64 00:02:54.240 --> 00:02:58.039 a second. Interacting with a computer purely through a graphical 65 00:02:58.080 --> 00:03:01.759 interface is basically like going to a restaurant and ordering 66 00:03:01.800 --> 00:03:03.800 off a fixed printed menu. 67 00:03:04.120 --> 00:03:05.520 Okay, yeah, I like that, right. 68 00:03:05.719 --> 00:03:07.879 You can choose the chicken, or you can choose the steak. 69 00:03:07.960 --> 00:03:10.280 You can maybe ask for the dressing on the side 70 00:03:10.479 --> 00:03:12.599 if they let you, exactly if they let you. But 71 00:03:12.719 --> 00:03:15.199 if you suddenly decide, hey, I want a fusion dish 72 00:03:15.199 --> 00:03:18.360 that isn't on the page, well, you are completely out 73 00:03:18.360 --> 00:03:18.759 of luck. 74 00:03:19.240 --> 00:03:22.719 That captures the limitation perfectly. You're trapped by the menu. 75 00:03:22.520 --> 00:03:26.199 But learning a programming language that feels like, I don't know, 76 00:03:26.319 --> 00:03:30.000 sneaking past the wait staff, walking straight into the restaurant's kitchen, 77 00:03:30.280 --> 00:03:32.879 finding where they keep all the raw ingredients, the pans, 78 00:03:32.919 --> 00:03:35.599 the spices, and just cooking whatever your heart desires. 79 00:03:35.840 --> 00:03:38.560 Yeah, taking control of the kitchen is the ultimate goal here, 80 00:03:39.000 --> 00:03:43.400 because to instruct a computer to perform truly open ended 81 00:03:43.719 --> 00:03:48.080 mavel tasks, you know, clicking buttons will never be enough. Right, 82 00:03:48.280 --> 00:03:50.439 We have to lean into our most powerful tool for 83 00:03:50.520 --> 00:03:54.879 abstract thought, which is language itself. Teaching a machine a 84 00:03:55.000 --> 00:03:58.879 language bypasses that fixed menu completely. 85 00:03:58.439 --> 00:04:01.759 Which honestly makes me wonder if if the shift to 86 00:04:01.879 --> 00:04:06.280 those incredibly easy, beautifully designed graphical interfaces actually made us 87 00:04:06.319 --> 00:04:09.759 forget how much raw power we hold over our devices. Oh, 88 00:04:09.759 --> 00:04:13.319 I think it absolutely did, because decades ago, interacting with 89 00:04:13.360 --> 00:04:16.839 a computer meant typing text onto a blank screen. There 90 00:04:16.920 --> 00:04:18.639 was no handholding none. 91 00:04:19.040 --> 00:04:23.240 We definitely traded absolute control for daily convenience, no question. 92 00:04:23.600 --> 00:04:26.600 But the raw power is still sitting right there, you know, 93 00:04:26.839 --> 00:04:30.079 just beneath the glossy surface of every app you use 94 00:04:30.279 --> 00:04:32.879 just waiting to be commanded. Yeah. In fact, the book 95 00:04:32.959 --> 00:04:36.120 highlights a quote from the computer scientist Joseph Weisenbaum that 96 00:04:36.240 --> 00:04:38.839 really sets the stakes for what we're talking about. He wrote, 97 00:04:39.279 --> 00:04:42.920 the computer programmer is a creator of universes for which 98 00:04:42.959 --> 00:04:45.839 he alone is responsible creator of universes. 99 00:04:45.879 --> 00:04:48.759 I mean, wow, you don't usually hear that kind of sweeping, 100 00:04:48.879 --> 00:04:52.199 majestic language applied to like someone typing lines of code 101 00:04:52.240 --> 00:04:53.040 in a dark room. 102 00:04:53.199 --> 00:04:57.680 It sounds grandiose, sure, but it's entirely accurate. Unlike physical engineering, 103 00:04:57.680 --> 00:04:59.720 where you have to worry about gravity, material costs for 104 00:05:00.000 --> 00:05:00.319 and all. 105 00:05:00.240 --> 00:05:02.240 That stuff real world problems, right. 106 00:05:02.120 --> 00:05:05.079 A computer program is completely costless to build. It is 107 00:05:05.120 --> 00:05:09.240 literally weightless. It grows and expands under your typing hands 108 00:05:09.439 --> 00:05:12.839 out of pure thought. Yeah, you are quite literally building 109 00:05:12.879 --> 00:05:17.040 a microscopic universe with virtually unlimited complexity. 110 00:05:17.399 --> 00:05:21.360 But a universe built out of pure thought sounds incredibly 111 00:05:21.399 --> 00:05:24.959 difficult to manage, like there's no physical scaffolding to keep 112 00:05:25.000 --> 00:05:27.759 it from collapsing in on itself exactly. And in the 113 00:05:27.759 --> 00:05:30.560 source material, the author even brings in a quote from 114 00:05:30.720 --> 00:05:33.560 Confucius to sort of warn us about this learning process. 115 00:05:33.839 --> 00:05:37.399 Confucius basically says uh, If I show you one corner 116 00:05:37.439 --> 00:05:39.519 of a square, you need to be anxious to go 117 00:05:39.680 --> 00:05:41.360 find the other three corners yourself. 118 00:05:41.439 --> 00:05:43.079 Yeah, he's setting expectations right. 119 00:05:43.120 --> 00:05:46.000 The author is giving us a heads up that digesting 120 00:05:46.040 --> 00:05:50.240 this material and building these universes it takes intense mental effort. 121 00:05:50.319 --> 00:05:53.000 It's like you're building a massive mental maze. 122 00:05:53.160 --> 00:05:55.560 The real danger of building a massive mental maze out 123 00:05:55.600 --> 00:05:58.800 of pure thought is that you can very easily get 124 00:05:58.879 --> 00:06:01.279 lost in it yourself. The complexity will just grow out 125 00:06:01.319 --> 00:06:02.720 of control if you aren't careful. 126 00:06:02.800 --> 00:06:03.879 So it's not just about typing. 127 00:06:04.600 --> 00:06:06.920 No, the true art of programming isn't really about typing 128 00:06:06.959 --> 00:06:09.040 the right words at all. It is the art of 129 00:06:09.079 --> 00:06:10.199 controlling complexity. 130 00:06:10.439 --> 00:06:13.519 Okay, So to control that complexity, we obviously have to 131 00:06:13.519 --> 00:06:15.399 start with the raw building blocks. We have to wade 132 00:06:15.439 --> 00:06:18.360 into what the book calls the sea of bits, and 133 00:06:18.399 --> 00:06:20.240 the scale of this is just hard to wrap your 134 00:06:20.240 --> 00:06:23.519 head around. A typical modern computer has more than thirty 135 00:06:23.560 --> 00:06:27.000 billion bits floating around in its volatile working memory. 136 00:06:26.959 --> 00:06:31.800 Thirty billion individual points of data and the bit it's 137 00:06:31.839 --> 00:06:35.079 the smallest conceivable unit of information. It only has two states, 138 00:06:35.240 --> 00:06:38.040 like on or off exactly. Think of it as a 139 00:06:38.079 --> 00:06:42.279 microscopic electrical switch that is either said to high or low. 140 00:06:43.000 --> 00:06:46.279 We represent those states conceptually as a one or a zero. 141 00:06:47.120 --> 00:06:48.879 And that is all. It is just an ocean of 142 00:06:48.920 --> 00:06:49.680 binary noise. 143 00:06:49.759 --> 00:06:52.319 Okay, but of everything is just an ocean of identical 144 00:06:52.399 --> 00:06:55.560 electrical charges. How does the computer know when a specific 145 00:06:55.639 --> 00:06:57.480 group of bits is supposed to be I don't know 146 00:06:57.519 --> 00:07:00.720 a number or a letter or a color like JavaScript 147 00:07:00.759 --> 00:07:03.399 would have to build fences inside that ocean. 148 00:07:03.759 --> 00:07:06.720 Building fences is exactly how it imposes order on the chaos. 149 00:07:07.240 --> 00:07:10.439 JavaScript takes that endless sea of thirty billion bits and 150 00:07:10.519 --> 00:07:13.720 chunks them into organized, manageable pieces of information. It calls 151 00:07:13.759 --> 00:07:17.120 them values value, and every single value you create is 152 00:07:17.120 --> 00:07:20.279 assigned a specific type, which then dictates exactly how the 153 00:07:20.279 --> 00:07:21.879 computer's allowed to interact with it. 154 00:07:22.120 --> 00:07:24.079 Let's look closely at the number type then, because I 155 00:07:24.079 --> 00:07:27.000 think this really illustrates how the physical reality of the 156 00:07:27.040 --> 00:07:31.000 machine actually limits the theoretical math it does. JavaScript draws 157 00:07:31.040 --> 00:07:34.560 a very specific fence for numbers. Right, It uses exactly 158 00:07:34.600 --> 00:07:38.199 sixty four bits to store a single number value. 159 00:07:37.879 --> 00:07:41.399 Meaning you have a physical container with exactly sixty four slots. 160 00:07:41.759 --> 00:07:44.439 Each slot can hold a one or a zero, And 161 00:07:44.480 --> 00:07:47.560 because it is a fixed physical size, well, there are 162 00:07:47.600 --> 00:07:50.319 only so many combinations of zeros and ones you can generate. 163 00:07:50.600 --> 00:07:54.040 I mean, sixty four bits still provides a massive playground 164 00:07:54.079 --> 00:07:56.439 doing the math on the combinations that gives you the 165 00:07:56.480 --> 00:08:00.519 ability to represent about eighteen quintillion different numbers. 166 00:08:00.600 --> 00:08:03.319 Yeah, that is an eighteen followed by eighteen zeros, which 167 00:08:03.360 --> 00:08:05.600 is huge. It feels like an infinite space, right, Ito 168 00:08:05.600 --> 00:08:07.319 likesy to count higher than you would ever need to 169 00:08:07.360 --> 00:08:11.360 in a lifetime. But it is fundamentally finite, right, not infinite. 170 00:08:11.399 --> 00:08:14.079 And because it is finite, the computer has to make compromises, 171 00:08:14.680 --> 00:08:17.160 especially when you ask it to store fractional numbers like 172 00:08:17.240 --> 00:08:18.759 say nine point eighty one. 173 00:08:19.199 --> 00:08:22.439 And this is where the physical architecture forces the computer 174 00:08:22.480 --> 00:08:24.600 to cheat a little bit, isn't it, Because out of 175 00:08:24.680 --> 00:08:27.680 those sixty four slots, one slot has to be reserved 176 00:08:27.839 --> 00:08:30.720 just to remember if the number is negative, then a 177 00:08:30.759 --> 00:08:32.759 whole chunk of slots has to be used to remember 178 00:08:32.799 --> 00:08:34.360 exactly where the decimal point. 179 00:08:34.200 --> 00:08:38.840 Lives, which leaves even fewer slots for the actual digits. So, 180 00:08:38.960 --> 00:08:40.960 just like the number pi goes on forever and can't 181 00:08:40.960 --> 00:08:44.159 be perfectly written out on a finite piece of paper. Oh, 182 00:08:44.200 --> 00:08:48.039 a computer can't store a complex, infinitely repeating fraction in 183 00:08:48.120 --> 00:08:51.360 a finite sixty four bit container. It physically runs out 184 00:08:51.360 --> 00:08:54.080 of room, so it simply rounds off the end. It 185 00:08:54.120 --> 00:08:57.159 basically just stores a very close approximation of the fraction. 186 00:08:57.399 --> 00:08:59.440 So as a programmer, you kind of have to look 187 00:08:59.480 --> 00:09:02.919 at fraction all digital numbers with a healthy dose of suspicion. 188 00:09:03.080 --> 00:09:06.519 Always they might be off by some microscopic, invisible fraction. 189 00:09:06.759 --> 00:09:09.960 But beyond the standard numbers, a JavaScript includes three special 190 00:09:10.039 --> 00:09:13.000 numbers inside the number type that are essentially like rebels. 191 00:09:13.279 --> 00:09:15.120 They don't follow the rules of normal math. 192 00:09:15.360 --> 00:09:18.440 Yeah. The first two are infinity and infinity, and they 193 00:09:18.480 --> 00:09:23.360 generally behave the way you would expect infinite concepts to behave, right, Like, 194 00:09:23.600 --> 00:09:26.919 if you subtract one from infinity, the result is still infinity. 195 00:09:27.000 --> 00:09:27.399 Makes sense. 196 00:09:27.440 --> 00:09:30.120 But if you start throwing infinity into your equations everywhere, 197 00:09:30.279 --> 00:09:34.399 the math starts getting very wobbly, very quickly, which leads 198 00:09:34.480 --> 00:09:39.399 to the third and probably most notorious special number, NAN, which. 199 00:09:39.240 --> 00:09:42.960 Literally stands for not a number. Okay, I have to 200 00:09:42.960 --> 00:09:45.279 stop and unpack this because it sounds like a cruel joke. 201 00:09:45.519 --> 00:09:46.000 It does. 202 00:09:46.360 --> 00:09:49.600 Why on Earth. Would a programming language explicitly create a 203 00:09:49.720 --> 00:09:53.080 value called not a number and then categorize it inside 204 00:09:53.120 --> 00:09:54.000 the number type. 205 00:09:54.279 --> 00:09:57.080 It sounds like a total paradox. I know, but you'd 206 00:09:57.159 --> 00:09:59.639 have to look at it from the computer's perspective. It 207 00:09:59.679 --> 00:10:01.120 needs a catch all safety net. 208 00:10:01.240 --> 00:10:02.039 A safety net. 209 00:10:02.159 --> 00:10:05.720 Yeah. If you force the computer to calculate something mathematically nonsensical, 210 00:10:05.759 --> 00:10:09.360 like zero divided by zero or infinite minus infinity, it 211 00:10:09.399 --> 00:10:10.919 has to return some kind of result. 212 00:10:11.120 --> 00:10:11.720 Oh, I see. 213 00:10:11.799 --> 00:10:13.960 It can't just return the number seven, because that's a lie. 214 00:10:14.039 --> 00:10:16.639 It can't return a word. It has to output a 215 00:10:16.799 --> 00:10:18.679 value of the number type. 216 00:10:18.480 --> 00:10:22.159 So it returns nan. It's essentially the computer throwing its 217 00:10:22.200 --> 00:10:25.039 hands up in the air, shrugging and saying, hey, I 218 00:10:25.120 --> 00:10:27.360 ran the calculation you asked for, but the result is 219 00:10:27.440 --> 00:10:28.399 complete gibberish. 220 00:10:28.720 --> 00:10:31.360 I tried, but this is nonsense exactly. 221 00:10:31.919 --> 00:10:34.919 It prevents the whole system from crashing just by providing 222 00:10:35.000 --> 00:10:38.039 a safe, predictable output for a broken equation. 223 00:10:38.480 --> 00:10:42.559 Okay. Moving beyond numbers, the language also chunks bits into 224 00:10:42.759 --> 00:10:46.679 other types. We have strings, which are used to represent text. 225 00:10:46.960 --> 00:10:49.519 You wrap your text in quote marks, and you can 226 00:10:49.559 --> 00:10:53.000 glue different strings together, which is a process called concatenation right, 227 00:10:53.519 --> 00:10:56.120 and then you have booleans, which are incredibly simply just 228 00:10:56.240 --> 00:10:58.679 act as logical true or false switches. 229 00:10:59.039 --> 00:11:02.039 You know. Taking a step back, the text provides some 230 00:11:02.200 --> 00:11:05.320 vital historical context that really makes you appreciate all these types. 231 00:11:05.399 --> 00:11:07.679 Oh yeah, the history is fascinating because in. 232 00:11:07.600 --> 00:11:11.159 The early days of computing, decades before JavaScript even existed, 233 00:11:11.519 --> 00:11:14.279 programmers did not have the luxury of just typing a 234 00:11:14.320 --> 00:11:16.080 word or a number. They had to act as the 235 00:11:16.120 --> 00:11:17.759 interface themselves. 236 00:11:17.279 --> 00:11:21.159 Literally flipping switches. Literally, they stood in front of massive 237 00:11:21.240 --> 00:11:26.039 machines and manually flipped large arrays of physical switches or 238 00:11:26.080 --> 00:11:29.679 punch tiny holes in cardboard cards just to feed those 239 00:11:29.720 --> 00:11:32.200 ones and zeros directly into the machine's memory. 240 00:11:32.360 --> 00:11:35.440 So you're basically doing the computer's job for it, manually 241 00:11:35.480 --> 00:11:40.000 calculating and arranging sixty four distinct electrical charges just to 242 00:11:40.039 --> 00:11:41.639 teach the machine the number thirteen. 243 00:11:42.080 --> 00:11:46.159 It was incredibly tedious, highly error prone work. Today, the 244 00:11:46.240 --> 00:11:50.039 JavaScript language handles all that translation invisibly. You type the 245 00:11:50.120 --> 00:11:53.879 number thirteen on your keyboard and the language instantly automatically 246 00:11:53.919 --> 00:11:56.879 generates the correct sixty four bit pattern and slots it 247 00:11:56.919 --> 00:11:58.039 into the computer's memory. 248 00:11:58.240 --> 00:12:01.320 It feels like magic when it works per But you know, 249 00:12:01.399 --> 00:12:03.600 as we teased at the very beginning of this steep dive, 250 00:12:03.720 --> 00:12:06.960 JavaScript is not a perfectly logical, predictable language. 251 00:12:07.000 --> 00:12:07.679 No it is not. 252 00:12:07.840 --> 00:12:10.799 It has a very specific, somewhat chaotic personality, and that 253 00:12:10.840 --> 00:12:13.919 personality actually comes from its history. It was created in 254 00:12:13.960 --> 00:12:16.159 a massive hurry back in nineteen ninety five for the 255 00:12:16.360 --> 00:12:18.039 Netscape Navigator web browser. 256 00:12:18.159 --> 00:12:21.720 Yeah, and even its name reflects that chaotic birth. The 257 00:12:21.799 --> 00:12:25.039 name JavaScript was purely a marketing ploy. Oh yeah, it 258 00:12:25.080 --> 00:12:29.919 has almost no actual relationship to the highly structured Java 259 00:12:29.960 --> 00:12:33.559 programming language that was incredibly popular at the time. Netscape 260 00:12:33.600 --> 00:12:36.240 just wanted to ride the codetails of Java's hype. 261 00:12:36.039 --> 00:12:40.720 Wow, and that rushed, heavily marketed design process led to 262 00:12:40.799 --> 00:12:45.240 some wild design choices. The source text notes that JavaScript 263 00:12:45.320 --> 00:12:48.440 was intentionally built to be highly forgiving, right. Yes, the 264 00:12:48.519 --> 00:12:51.840 creators wanted it to be accessible for total beginners. The 265 00:12:51.879 --> 00:12:55.120 philosophy was basically that the language should accept almost anything 266 00:12:55.120 --> 00:12:57.639 you type, no matter how badly formatted, without crashing the 267 00:12:57.639 --> 00:12:58.240 web browser. 268 00:12:58.559 --> 00:13:02.039 And I mean, on the surface, a language that refuses 269 00:13:02.039 --> 00:13:05.919 to crash sounds like a beginner's dream, but in practice, 270 00:13:06.000 --> 00:13:08.240 a language that refuses to crash is a language that 271 00:13:08.279 --> 00:13:11.200 refuses to tell you when you've made a catastrophic mistake right. 272 00:13:11.240 --> 00:13:13.480 It hides your errors from you. Instead of stopping the 273 00:13:13.480 --> 00:13:15.919 program and saying, hey, line forty two, it makes no sense, 274 00:13:15.960 --> 00:13:19.440 please fix it, JavaScript decides to just quietly play along. 275 00:13:19.639 --> 00:13:21.639 He uses a process called type coercion. 276 00:13:21.720 --> 00:13:25.000 Type coercion it basically looks at your bad code and 277 00:13:25.080 --> 00:13:28.799 tries to guess your underlying intent. It literally forces one 278 00:13:28.879 --> 00:13:31.200 type of data to become another type of data, so 279 00:13:31.240 --> 00:13:32.679 the equation could just finish. 280 00:13:33.080 --> 00:13:36.320 I love the analogy for this. JavaScript acts exactly like 281 00:13:36.360 --> 00:13:40.279 an overly eager improv comedy partner. Yes, the improv partner, 282 00:13:40.320 --> 00:13:43.679 because the golden rule of improv is yes, and you 283 00:13:43.759 --> 00:13:45.320 never shut down your partner's idea. 284 00:13:45.440 --> 00:13:45.600 Right. 285 00:13:45.679 --> 00:13:48.759 You accept whatever crazy scenario they introduce, and you build 286 00:13:48.840 --> 00:13:50.960 on it. Exactly if you say, hey, I brought a 287 00:13:51.000 --> 00:13:53.600 toaster to the beach, your partner doesn't say that makes 288 00:13:53.600 --> 00:13:56.320 no sense. They say yes, and the toaster is actually 289 00:13:56.360 --> 00:13:57.919 a submarine. 290 00:13:57.279 --> 00:14:00.799 That captures the dynamic perfectly. It keeps the scene moving 291 00:14:00.840 --> 00:14:03.679 forward at all costs, even if you are no longer 292 00:14:03.720 --> 00:14:05.399 in the scene you originally intended to. 293 00:14:05.399 --> 00:14:07.879 Write let's walk through the hilarious examples of this from 294 00:14:07.879 --> 00:14:12.080 the book You Hand JavaScript and equation. Like the number 295 00:14:12.120 --> 00:14:16.919 eight multiplied by null. Now NOLL basically means emptiness nothing. 296 00:14:17.480 --> 00:14:20.600 Instead of crashing, JavaScript says, oh, you want to multiply, Well, 297 00:14:20.639 --> 00:14:22.679 nol is kind of like the number zero yes, and 298 00:14:22.840 --> 00:14:24.240 eight times zero zero zero. 299 00:14:24.720 --> 00:14:28.000 It just quietly converted the concept of emptiness into a 300 00:14:28.039 --> 00:14:29.399 mathematical integer. 301 00:14:29.240 --> 00:14:31.639 And it gets so much weirder. The text points out 302 00:14:31.639 --> 00:14:34.480 that if you take the string five, the actual text 303 00:14:34.600 --> 00:14:36.799 character of a five, and you try to subtract the 304 00:14:36.879 --> 00:14:40.240 number one from it, JavaScript says, well, you obviously can't 305 00:14:40.279 --> 00:14:42.840 subtract numbers from a word, so you must have accidentally 306 00:14:42.840 --> 00:14:45.720 put quotes around the number five. Yes, and five minus 307 00:14:45.759 --> 00:14:46.360 one is four. 308 00:14:46.919 --> 00:14:49.159 It converts the text string into a number type to 309 00:14:49.200 --> 00:14:52.879 make the math work out, which I mean admittedly feels 310 00:14:52.879 --> 00:14:53.879 somewhat intuitive. 311 00:14:54.200 --> 00:14:56.399 But then you try the exact opposite. You take the 312 00:14:56.440 --> 00:14:59.120 string five and you add the number one. A human 313 00:14:59.159 --> 00:15:03.320 would assume the end six naturally, but JavaScript sees the 314 00:15:03.320 --> 00:15:06.240 plus sign and says, oh, a plus sign. You don't 315 00:15:06.240 --> 00:15:08.399 want to do math, you want to glue things together, 316 00:15:08.679 --> 00:15:11.120 So it converts the number one into text, glues it 317 00:15:11.159 --> 00:15:13.879 to the text five, and confidently hands you back the 318 00:15:13.879 --> 00:15:14.919 string fifty one. 319 00:15:15.080 --> 00:15:19.080 It is applying an absolute literal logic to the symbols 320 00:15:19.080 --> 00:15:21.840 you typed, completely blind to the fact that the result 321 00:15:21.919 --> 00:15:24.559 is total nonsense to a human reader. And if you 322 00:15:24.639 --> 00:15:27.799 push it too far, say trying to multiply this spelled 323 00:15:27.799 --> 00:15:31.279 out word five by the number two, it finally realizes 324 00:15:31.360 --> 00:15:34.919 it cannot convert letters into math. So rather than crashing, 325 00:15:35.240 --> 00:15:39.600 it hands you back our old friend nan, not a number. 326 00:15:39.960 --> 00:15:42.879 So, as a programmer trying to build a stable universe, 327 00:15:43.320 --> 00:15:45.919 how do you defend yourself against an improv partner who 328 00:15:45.960 --> 00:15:48.240 constantly alters reality behind your back. 329 00:15:48.480 --> 00:15:50.559 Well, you have to strip away its ability to guess. 330 00:15:50.960 --> 00:15:54.679 You have to be incredibly explicit. The language provides defense 331 00:15:54.720 --> 00:15:57.720 mechanisms for this, thankfully, Like what for example, when you 332 00:15:57.759 --> 00:16:00.000 want to check if two things are equal, you don't 333 00:16:00.120 --> 00:16:02.360 use the standard double equal sign. You use the strictly 334 00:16:02.360 --> 00:16:05.080 equal operator, which is three equal signs in a row. 335 00:16:05.200 --> 00:16:07.039 Oh, so it's like a strict bouncer at the door. 336 00:16:07.120 --> 00:16:10.559 Precisely that triple equal sign tells JavaScript, do not do 337 00:16:10.639 --> 00:16:13.120 any automatic type conversions, do not try to guess what 338 00:16:13.159 --> 00:16:15.799 I meant only return true if these two items are 339 00:16:15.799 --> 00:16:18.039 the exact same type and the exact same value. 340 00:16:18.159 --> 00:16:20.120 So no improbable out none good. 341 00:16:20.320 --> 00:16:24.759 And Another fascinating defense mechanism is exploiting the language's natural 342 00:16:24.840 --> 00:16:27.799 laziness through something called short circuit evaluation. 343 00:16:28.279 --> 00:16:33.120 Short circuit evaluation that sounds incredibly abstract. How do you 344 00:16:33.200 --> 00:16:35.279 exploit laziness in a machine? 345 00:16:35.480 --> 00:16:39.279 Let's translate out of code. Imagine a bouncer at an 346 00:16:39.320 --> 00:16:43.879 exclusive club. Okay, the rule is you can come inside 347 00:16:44.120 --> 00:16:46.320 if you are on the VIP list, or if you 348 00:16:46.360 --> 00:16:49.639 pay one hundred dollars cover charge. You walk up and 349 00:16:49.679 --> 00:16:52.720 the bouncer sees your name on the VIP list. At 350 00:16:52.759 --> 00:16:55.279 that exact moment, does he ask you if you have 351 00:16:55.320 --> 00:16:56.080 one hundred dollars? 352 00:16:56.360 --> 00:16:58.720 No, he doesn't care. The first condition was met, so 353 00:16:58.759 --> 00:17:00.879 he just opens the door or circuits the rest of 354 00:17:00.919 --> 00:17:02.000 the question exactly. 355 00:17:02.159 --> 00:17:05.799 JavaScript handles logical or statements the exact same way. If 356 00:17:05.839 --> 00:17:08.279 you give it an equation that says true r x, 357 00:17:08.680 --> 00:17:11.279 JavaScript seedes that the first part is true, the overall 358 00:17:11.319 --> 00:17:13.759 statement is already satisfied. Oh wow, so it never even 359 00:17:13.799 --> 00:17:16.720 looks at X. It completely ignores whatever code is written there. 360 00:17:17.119 --> 00:17:19.319 X could be a terrible error that would normally crash 361 00:17:19.359 --> 00:17:22.039 the program, but JavaScript is too lazy to read it, 362 00:17:22.160 --> 00:17:23.519 so your program survives. 363 00:17:23.799 --> 00:17:26.839 That is a brilliant way to conceptualize it. So we've 364 00:17:26.839 --> 00:17:29.279 spent all this time talking about values floating in the 365 00:17:29.279 --> 00:17:32.079 sea of bits and how they combine into equations. The 366 00:17:32.119 --> 00:17:36.440 book calls these combinations expressions. But an expression sort of 367 00:17:36.480 --> 00:17:40.680 feels like a sentence fragment. Just calculating five plus five 368 00:17:40.839 --> 00:17:43.759 produces the value ten, but it doesn't actually do anything. 369 00:17:43.880 --> 00:17:47.160 Think of an expression like the computer daydreaming. It thinks 370 00:17:47.160 --> 00:17:50.119 to itself five plus five is ten, but it keeps 371 00:17:50.160 --> 00:17:52.160 that thought entirely in its own head. 372 00:17:52.680 --> 00:17:53.440 Oh okay. 373 00:17:53.599 --> 00:17:56.799 To actually change the state of the machine, we need 374 00:17:56.920 --> 00:18:00.400 what the book calls a statement. A statement is full 375 00:18:00.480 --> 00:18:04.079 complete sentence. It crosses the boundary from digital thought into 376 00:18:04.079 --> 00:18:06.759 physical reality by creating a side effect. 377 00:18:06.960 --> 00:18:09.880 A side effect that's the computer finally opening its mouth 378 00:18:09.920 --> 00:18:12.559 to speak. Basically, it pops a dialogue box up on 379 00:18:12.599 --> 00:18:14.599 your screen, or it reaches out and saves a file 380 00:18:14.640 --> 00:18:16.079 to your hard drive exactly. 381 00:18:16.640 --> 00:18:19.519 But to have meaningful side effects over time, the program 382 00:18:19.559 --> 00:18:22.839 cannot just react in the moment. It needs an internal memory. 383 00:18:22.880 --> 00:18:24.920 It needs to keep track of its own state, and 384 00:18:24.960 --> 00:18:26.640 we achieve this using variables. 385 00:18:27.000 --> 00:18:29.640 And here is a crucial mental shift the author demands 386 00:18:29.680 --> 00:18:32.720 from the reader. Anyone who has gabbled encrding is usually 387 00:18:32.720 --> 00:18:35.039 taught that a variable is like a little cardboard box 388 00:18:35.039 --> 00:18:36.480 where you store a piece of data. 389 00:18:36.559 --> 00:18:38.480 Right, that's the classic teaching tool, right. 390 00:18:38.680 --> 00:18:42.440 But the book consists that variables are absolutely not boxes. 391 00:18:42.640 --> 00:18:43.759 They are tentacles. 392 00:18:44.240 --> 00:18:48.960 It is such a visceral, accurate metaphor. Really, Yeah, variables 393 00:18:48.960 --> 00:18:51.200 do not contain values. They grasp them. 394 00:18:51.279 --> 00:18:52.079 They grasp them. 395 00:18:52.200 --> 00:18:56.920 Yeah. Picture a massive, invisible octopus living inside your computer's memory. 396 00:18:57.799 --> 00:19:00.079 When you define a new variable, you are commanding the 397 00:19:00.079 --> 00:19:02.839 program to grow a new tentacle, reach out into the 398 00:19:02.880 --> 00:19:06.079 sea of bits and hold tightly onto a specific value. 399 00:19:06.200 --> 00:19:08.799 Okay, Let's say I create a variable called Luji's debt 400 00:19:08.880 --> 00:19:11.000 and I tell the program his debt is one hundred 401 00:19:11.000 --> 00:19:14.240