1 00:00:00,750 --> 00:00:06,610 All right guys so I think now that you know functions are in you know loops and if statements I think 2 00:00:06,610 --> 00:00:09,020 it that now it's time to talk about scope. 3 00:00:09,210 --> 00:00:16,590 Okay I wanted to talk about scope because of LET and Konst versus Vire earlier but for those of you 4 00:00:16,590 --> 00:00:21,420 that didn't know what a function was or how it was set up or if statements I didn't want to go over 5 00:00:21,420 --> 00:00:21,840 it yet. 6 00:00:21,840 --> 00:00:25,300 So now that we've already done that let's talk about scope. 7 00:00:25,300 --> 00:00:33,100 So what I'm going to do is create a couple of variables and just tell you that this is the global scope. 8 00:00:33,150 --> 00:00:36,800 OK we're not inside of anything any functions or anything like that. 9 00:00:36,800 --> 00:00:38,360 This is the global scope. 10 00:00:38,460 --> 00:00:44,300 I'm going to set three variables using all three methods so var A equals. 11 00:00:44,850 --> 00:00:48,900 And we'll just say well it's just two numbers. 12 00:00:48,900 --> 00:00:50,240 We'll just do one. 13 00:00:50,520 --> 00:01:00,980 So var equals 1 and then we'll do a let B equals two and then we'll do a contest C equals three. 14 00:01:01,370 --> 00:01:15,960 OK and then down here will Konsole dot log and we'll say global scope A B C and save and you can see 15 00:01:15,960 --> 00:01:17,870 global scope 1 2 3. 16 00:01:17,870 --> 00:01:19,840 So this is var A. 17 00:01:19,860 --> 00:01:21,070 This is. 18 00:01:21,150 --> 00:01:21,780 Let be. 19 00:01:21,780 --> 00:01:26,670 This is Conte's see OK so everything's fine that's what you would expect. 20 00:01:26,670 --> 00:01:28,320 Now let's do a function. 21 00:01:28,400 --> 00:01:31,250 So say function test. 22 00:01:31,680 --> 00:01:40,640 And let's again define three variables except they're going to change the value to 5 not 5 for that. 23 00:01:40,890 --> 00:01:52,040 So 4 5 and 6 and then we're going to just console log in here and this time let's say function scope 24 00:01:52,610 --> 00:01:54,610 and let's see what we get. 25 00:01:54,620 --> 00:01:55,900 Hope we get to run the function 26 00:01:58,750 --> 00:01:59,180 OK. 27 00:01:59,190 --> 00:02:06,030 So function scope we get four five and six global scope we get 1 2 and 3. 28 00:02:06,030 --> 00:02:12,820 So basically these are these are separate variables than these are because they're in a different scope. 29 00:02:13,020 --> 00:02:13,470 OK. 30 00:02:13,470 --> 00:02:14,940 See how that works. 31 00:02:14,940 --> 00:02:19,080 Var is of a function scope declaration. 32 00:02:19,080 --> 00:02:26,090 Meaning that you can have a different a different variable of the same name inside of a function. 33 00:02:26,250 --> 00:02:27,420 Then on the outside. 34 00:02:27,420 --> 00:02:30,100 So this is going to affect this. 35 00:02:30,330 --> 00:02:34,600 Now we also have something called block level scope. 36 00:02:34,670 --> 00:02:38,240 But what I mean by block is an if statement a loop. 37 00:02:38,250 --> 00:02:47,070 Anything that is wrapped in curly braces so let's put an if statement here and it doesn't matter what 38 00:02:47,070 --> 00:02:48,820 we put in here let's just say true. 39 00:02:48,820 --> 00:02:50,730 So it definitely runs. 40 00:02:50,880 --> 00:02:56,440 And then we're going to put a comment here and this is a block scope. 41 00:02:56,820 --> 00:02:57,490 OK. 42 00:02:57,550 --> 00:03:07,270 And we'll take these variables and we're going to set them to 4 5 and 6 and then let's do a console 43 00:03:07,290 --> 00:03:18,090 log within the if and we'll say or let's say if scope it is a Blasko but we'll just say f and save and 44 00:03:18,090 --> 00:03:19,010 let's see what happens. 45 00:03:19,010 --> 00:03:24,830 So this is the scope we get four five and six which is fine. 46 00:03:24,870 --> 00:03:27,830 Now look at the global scope global scope. 47 00:03:27,830 --> 00:03:30,450 We have four to three. 48 00:03:30,480 --> 00:03:37,050 So what's happened is we defined a in the global scope and then within the if scope or within the block 49 00:03:37,050 --> 00:03:45,300 scope of the if statement that a variable was changed because when we Eckl or when we Konsole log it 50 00:03:45,300 --> 00:03:52,810 out back in the global scope it's changed to 4 where it was assigned inside of the half. 51 00:03:53,060 --> 00:03:53,540 OK. 52 00:03:53,550 --> 00:03:56,790 Notice leten Konst is still 2 and 3. 53 00:03:56,970 --> 00:04:01,950 Even though inside the block scope we set them to 5 and 6 they're still in there still two and three 54 00:04:01,950 --> 00:04:05,810 in the global scope because that's what we initially declared them as. 55 00:04:06,000 --> 00:04:12,540 So the way that Latin cons to work is how most programming languages work. 56 00:04:12,660 --> 00:04:19,500 Vire what is kind of weird and then it's one of the things that a lot of people didn't like about javascript 57 00:04:20,150 --> 00:04:27,300 because of security Caesarians causes security risks and it can just cause confusion if you have some 58 00:04:27,300 --> 00:04:34,650 variable in the global scope and then inside a block some program has the same variable name. 59 00:04:34,650 --> 00:04:36,500 Things can get messed up. 60 00:04:36,540 --> 00:04:39,260 So let's now try this with a loop. 61 00:04:39,640 --> 00:04:43,970 OK so we're going to do a for loop. 62 00:04:44,390 --> 00:04:45,150 All right. 63 00:04:45,200 --> 00:04:48,290 And what I'm going to do is I'm going to first use let. 64 00:04:48,380 --> 00:05:03,110 OK so I'm going to say Let let's do let a he calls 0 and then we'll say as long as a is less than 10 65 00:05:03,800 --> 00:05:11,580 and then we'll do a plus plus and then console dog log. 66 00:05:11,640 --> 00:05:16,790 They actually put a template string in here and it's a loop 67 00:05:19,810 --> 00:05:22,930 say loop and save. 68 00:05:22,940 --> 00:05:28,250 All right so each value for a in the loop is going to be 0 1 2 all the way up to 9. 69 00:05:28,430 --> 00:05:36,970 But in the global scope a success shouldn't that be since I did let be here. 70 00:05:37,070 --> 00:05:42,290 Well no actually that doesn't matter doesn't matter because we said we set a to one here whether it's 71 00:05:42,290 --> 00:05:43,610 fire or let. 72 00:05:43,610 --> 00:05:46,050 What matters is that we're using LET here. 73 00:05:46,280 --> 00:05:48,160 So it's stayed as one. 74 00:05:48,440 --> 00:05:49,210 OK. 75 00:05:49,250 --> 00:05:52,020 If I were to use var here. 76 00:05:53,120 --> 00:05:55,890 OK remember the global scope it's one with LET. 77 00:05:55,970 --> 00:05:57,360 If I use var. 78 00:05:57,530 --> 00:05:59,900 Look at that it changes to 10. 79 00:05:59,930 --> 00:06:08,210 OK so the loop the variable A in the loop since we use if our actually changes the value of the global 80 00:06:08,220 --> 00:06:10,500 A which is not good. 81 00:06:10,640 --> 00:06:16,180 OK so that's that's another reason that leten cons two are created. 82 00:06:16,580 --> 00:06:25,540 So hopefully that gives you an understanding of scope and how leten Konst are different than far left 83 00:06:25,710 --> 00:06:31,220 and Konst have a block level scope and var has a function scope.