1
00:00:00,180 --> 00:00:04,950
You might also get another question regarding the selection of JavaScript here.

2
00:00:04,970 --> 00:00:09,690
We must create the premise function to be able to use callback function via promise.

3
00:00:10,590 --> 00:00:15,990
And actually, just for you to know, previously we had a lot of callback functions because we didn't

4
00:00:15,990 --> 00:00:16,800
have promises.

5
00:00:17,100 --> 00:00:23,370
Then after some time in JavaScript, we migrated fully to promises and now they're supported in JavaScript

6
00:00:23,370 --> 00:00:27,570
by default, which actually means we're not using callbacks that much anymore.

7
00:00:27,870 --> 00:00:33,390
And as you can see here, we have a standard callback function where inside word doing some asynchronous

8
00:00:33,390 --> 00:00:39,120
code and we must write this function to prime this approach, which actually means, for example, we're

9
00:00:39,120 --> 00:00:45,480
using some older library which is based on the callbacks, but the whole code of our project is using

10
00:00:45,480 --> 00:00:46,110
premises.

11
00:00:46,320 --> 00:00:51,510
This is why it makes a lot of sense to make a wrapper and to use this callback function through the

12
00:00:51,510 --> 00:00:52,020
premise.

13
00:00:55,170 --> 00:01:00,990
To do this, we must create a theme which is called promise by function, which actually means the same

14
00:01:00,990 --> 00:01:06,000
function, but wrapped in promise so we can name it from me sci fi.

15
00:01:06,210 --> 00:01:07,710
And this is the typical name in.

16
00:01:08,340 --> 00:01:09,510
I think, fun.

17
00:01:09,840 --> 00:01:13,440
Just like on the top and here, we don't have any arguments.

18
00:01:13,770 --> 00:01:16,860
And inside here we want to call out a sync function.

19
00:01:17,070 --> 00:01:21,450
And when we have a callback, then we want to call our callback from the premise.

20
00:01:21,720 --> 00:01:24,360
This is where here we must return and you promise.

21
00:01:24,600 --> 00:01:30,390
And here inside promise, we have resolve and rechecked, but we will use here on the result because

22
00:01:30,410 --> 00:01:32,010
we don't have any error here.

23
00:01:32,400 --> 00:01:38,430
Now, inside our promise, we can just call the regular icing function and put the call back inside.

24
00:01:38,700 --> 00:01:41,460
And actually, this callback will give us some data back.

25
00:01:41,670 --> 00:01:47,100
This is why here I am right in data and we even don't know what data we're talking about now.

26
00:01:47,100 --> 00:01:53,070
Inside, we want just to cold resolve and Boston site data from our asynchronous function.

27
00:01:53,250 --> 00:01:58,230
In this case, when the synchronous function is done, then our callback will be happening.

28
00:01:58,470 --> 00:02:03,960
And here, insert callback, we're getting data from asynchronous function and we're calling in callback

29
00:02:03,960 --> 00:02:06,720
resolve for this promise that we created.

30
00:02:07,050 --> 00:02:10,590
And most importantly, that this function will return a promise.

31
00:02:10,920 --> 00:02:12,330
This is why we can use it now.

32
00:02:12,330 --> 00:02:13,580
Like this promise?

33
00:02:13,590 --> 00:02:17,370
If I think function, we just call it and it returns as a.

34
00:02:18,120 --> 00:02:19,500
This is why we can right here.

35
00:02:19,500 --> 00:02:24,450
Then we're getting some result and we can do, for example, console.log result.

36
00:02:24,810 --> 00:02:31,150
So we're using this function as a promise, and we've wrapped our async function in promise ify.

37
00:02:31,230 --> 00:02:32,160
Let's check this out.

38
00:02:32,310 --> 00:02:37,740
I'm deployed in the page and as you can see, we're getting back one after some time because here we

39
00:02:37,740 --> 00:02:43,140
have callback with three thousand milliseconds, which actually means we're getting our data after three

40
00:02:43,140 --> 00:02:45,330
seconds and this code is working.

41
00:02:45,480 --> 00:02:51,210
And now everyone in our application, we can use this callback function in promise of triage.