1 00:00:00,600 --> 00:00:05,910 The last hope that we will talk about is called lexical scope. 2 00:00:05,939 --> 00:00:07,750 So what is laser scope? 3 00:00:07,770 --> 00:00:10,200 So let me comment this once. 4 00:00:11,340 --> 00:00:20,280 Now bring the function scope down here and change this one to less lexical scope. 5 00:00:20,310 --> 00:00:22,530 Okay, so save it. 6 00:00:22,530 --> 00:00:23,860 And there we go. 7 00:00:23,880 --> 00:00:25,290 Okay, a little bit. 8 00:00:25,290 --> 00:00:25,790 A little bit. 9 00:00:25,800 --> 00:00:26,420 A little bit. 10 00:00:26,430 --> 00:00:27,660 Yeah. 11 00:00:27,690 --> 00:00:28,150 Good. 12 00:00:28,170 --> 00:00:31,140 So what is lexical scope in JavaScript? 13 00:00:31,440 --> 00:00:39,390 It refers to the visibility of variables and functions in relation to the lexical structure of the code. 14 00:00:39,420 --> 00:00:41,330 That is the scope of a variable. 15 00:00:41,340 --> 00:00:45,690 A function is determined by H position in the code. 16 00:00:45,780 --> 00:00:52,590 For example, variables in function declared inside a function are only visible inside that function. 17 00:00:52,590 --> 00:00:53,730 That one we know. 18 00:00:53,820 --> 00:01:01,410 And again, lexical scope is an important concept in JavaScript because it affects how code is executed 19 00:01:01,410 --> 00:01:03,600 and how variables are accessed. 20 00:01:04,050 --> 00:01:10,830 But this is also a complex topic again, so and there are a few different ways to think about it. 21 00:01:11,160 --> 00:01:12,510 But let me break it down. 22 00:01:13,500 --> 00:01:19,090 One way to think about lexical scope is in terms of the nesting of functions. 23 00:01:19,110 --> 00:01:26,700 I mean, we are going to nest a function together and see how we can access variables across these nested 24 00:01:26,700 --> 00:01:27,510 functions. 25 00:01:27,600 --> 00:01:34,620 So the scope of the inner function is said to be lexical and close by the scope of the outer function. 26 00:01:34,620 --> 00:01:42,090 And this means that the inner function has access to variables and functions declared in the outer function, 27 00:01:42,090 --> 00:01:44,050 but not vice versa. 28 00:01:44,070 --> 00:01:47,580 So let me prove you something here about lexical scope. 29 00:01:47,970 --> 00:01:56,040 For this one, we are going to next function together and see if we can access variables both the nested 30 00:01:56,040 --> 00:01:57,390 and the outer function. 31 00:01:57,650 --> 00:01:58,130 Great. 32 00:01:58,140 --> 00:02:00,240 So let's declare a function. 33 00:02:00,240 --> 00:02:02,760 Let's say my function one. 34 00:02:03,920 --> 00:02:04,550 All right. 35 00:02:04,550 --> 00:02:07,670 And dysfunction will not take anything great. 36 00:02:08,240 --> 00:02:12,530 And inside this function, let's also declare other functions inside. 37 00:02:12,530 --> 00:02:17,330 So function is going to be another function. 38 00:02:17,420 --> 00:02:23,060 Remember, because functions are first class citizens, we can pass a function, a function, and we 39 00:02:23,060 --> 00:02:24,950 can return a function from a function. 40 00:02:25,370 --> 00:02:30,170 After this one, we are going to dive more about how we can create a function. 41 00:02:30,890 --> 00:02:33,800 So let's say we have a function called another function. 42 00:02:33,800 --> 00:02:39,710 Being inside my function and I has that and this a perfect function call. 43 00:02:39,710 --> 00:02:47,210 So let's say that inside my outer function of my inner function, I'm going to declare a variable C. 44 00:02:47,240 --> 00:02:48,710 S, which represents. 45 00:02:48,710 --> 00:02:49,340 Hello. 46 00:02:50,250 --> 00:02:51,120 As that. 47 00:02:51,360 --> 00:02:57,150 And inside the honor function, I'm also going to declare a variable, say y. 48 00:02:57,180 --> 00:03:02,220 So let's say here, let's y also equal to let's say ten. 49 00:03:02,610 --> 00:03:03,390 Perfect. 50 00:03:03,960 --> 00:03:09,480 So let's try to console.log the x in my first function. 51 00:03:10,130 --> 00:03:12,680 Now let's call this function down here. 52 00:03:12,830 --> 00:03:16,400 It's going to be my function one if I save it. 53 00:03:16,430 --> 00:03:18,750 Now, you see, I have. 54 00:03:18,770 --> 00:03:19,460 Hello. 55 00:03:20,060 --> 00:03:23,240 So how can you also call this function? 56 00:03:23,810 --> 00:03:24,980 This function here? 57 00:03:25,890 --> 00:03:26,760 Dysfunction. 58 00:03:27,580 --> 00:03:29,650 Because it is his cope with this one. 59 00:03:29,650 --> 00:03:33,370 We can also call the function inside my first function. 60 00:03:33,370 --> 00:03:39,630 So call, function or invoke for short in work. 61 00:03:39,640 --> 00:03:44,710 So this one too let's console.log the y and let's see. 62 00:03:44,710 --> 00:03:50,930 So now see that this function has been called, but this one hasn't been called because we haven't invoked 63 00:03:50,930 --> 00:03:51,700 the function. 64 00:03:51,820 --> 00:03:55,810 So come down here, let's say another function, call it. 65 00:03:55,960 --> 00:03:56,710 Let's save it. 66 00:03:56,710 --> 00:04:01,990 Now I have the two functions being called, but here we go. 67 00:04:02,260 --> 00:04:05,710 Even though we have a function scope here. 68 00:04:06,160 --> 00:04:09,850 But inside this function we have two things going on. 69 00:04:09,850 --> 00:04:14,290 We have a variable here and we have another function here. 70 00:04:14,710 --> 00:04:24,490 So a variable that we declared outside this function which is X can be accessed inside my inner function. 71 00:04:24,580 --> 00:04:25,510 Have a look. 72 00:04:25,540 --> 00:04:30,970 If I try to console.log x, let's console.log x, k and let's see. 73 00:04:30,970 --> 00:04:33,160 Now everything works fine. 74 00:04:33,160 --> 00:04:37,210 Line number 54, which is this line of T four. 75 00:04:37,660 --> 00:04:38,770 So it works. 76 00:04:38,800 --> 00:04:48,910 But if I try to access this Y outside this function inside my outer function here, so let me change 77 00:04:48,910 --> 00:04:51,160 this one to Y now let's see. 78 00:04:51,160 --> 00:04:53,530 Now I get an error. 79 00:04:53,530 --> 00:04:57,190 So take note about this again. 80 00:04:57,460 --> 00:05:05,020 A variable that we declared outside the inner function can be declared or can be console.log or can 81 00:05:05,020 --> 00:05:08,770 be found or can be used inside the inner function. 82 00:05:09,250 --> 00:05:17,740 But a variable declared inside my inner function cannot be accessed outside the inner function. 83 00:05:17,890 --> 00:05:20,650 That's about the physical scope.