JS (in ES6) sync & await understanding

async function fun(){
    
    console.log("2");
    let a = await 7;
    console.log("4");
    let b = await new Promise((resolve,reject)=>{
    
        setTimeout(function(){
    
            resolve('setTimeout')
        },3000)
    })
    console.log("5");
    let c = await function(){
    
        return 'function'
    }()
    console.log("6")
    console.log(a,b,c)
    console.log("8")
}
console.log("1")
fun(); // 3 Second output ： 7 "setTimeout" "function"
console.log("3")

 Running results :
1
2
3
4
 appear :undefined The variable of , finger b
---
     stop 3 second 
----
5
6
7 'setTimeout' 'function'
8

thus it can be seen js(ES6 standard ) in async And await The running order of

Here first mark, Borrow a book another day , Multi research , Elaborate its principle ( Single thread ,js Run stack , browser API, Polling mechanism ,
from io Delay –> Synchronous and asynchronous requirements –> Several implementations of asynchrony : Callback function -- Callback hell problem leads to –>promise,then —>async+await,js The final solution of asynchrony )
Recently, I finished the small program development !

Thinking inspiration :
Find out in a few minutes Promise, Async, Await Usage of

async/await Understanding and usage of