1
00:00:01,060 --> 00:00:01,820
Hello friends!

2
00:00:01,840 --> 00:00:03,100
Nice to see you back.

3
00:00:03,130 --> 00:00:08,950
In this tutorial we are going to learn two new features of JavaScript async and await.

4
00:00:08,980 --> 00:00:14,890
Let's try to explore what is async function as we make normal functions.

5
00:00:14,890 --> 00:00:16,960
In our case test.

6
00:00:16,990 --> 00:00:23,260
If I type async keyword before the function keyword, then it will become a async function.

7
00:00:23,260 --> 00:00:28,840
But the question is what is the difference between a normal function and a async function?

8
00:00:28,870 --> 00:00:34,600
Async function always return a promise, and we learn about promise in our previous videos.

9
00:00:34,600 --> 00:00:35,950
And we know promise.

10
00:00:35,950 --> 00:00:38,980
Return two type of function resolve and reject.

11
00:00:38,980 --> 00:00:41,410
Based on this we do our further work.

12
00:00:41,410 --> 00:00:47,590
If it resolve, then we call then function, and if our promise is rejected, then automatically call

13
00:00:47,590 --> 00:00:48,670
catch function.

14
00:00:48,670 --> 00:00:51,820
So our async function work like promise.

15
00:00:51,850 --> 00:00:53,970
It may be resolve or reject.

16
00:00:53,980 --> 00:00:59,650
Similarly, we can call then function for resolve and we can call catch function for reject.

17
00:00:59,680 --> 00:01:06,490
Now the question is why we use the async function since we already have the promise method.

18
00:01:06,490 --> 00:01:10,630
If you remember, there is a little complication in our promise method.

19
00:01:10,930 --> 00:01:15,310
Every time we need to declare, resolve, or reject function in promise.

20
00:01:15,520 --> 00:01:20,230
To resolve this kind of complication, JavaScript introduce async function.

21
00:01:20,230 --> 00:01:22,450
It is very easy to operate just.

22
00:01:22,450 --> 00:01:28,510
You need to type async keyword before the function keyword, and you don't need to change in your function.

23
00:01:28,510 --> 00:01:35,350
And I want to tell one thing our promise function introduced in JavaScript, ES6 version and async function

24
00:01:35,350 --> 00:01:39,550
introduce in JavaScript is 2017 version.

25
00:01:39,550 --> 00:01:44,260
From here you can understand why JavaScript introduced async function.

26
00:01:44,290 --> 00:01:47,620
The answer is simple to resolve, promise, complication.

27
00:01:47,620 --> 00:01:53,410
All the things that we could do inside the promise method we can do in async function.

28
00:01:53,410 --> 00:01:57,370
So without wasting your time, let's back to the Visual Studio Code Editor.