How async await implements concurrency

I still remember my internship in autumn last year , The second interviewer, brother long ( The current team leader ) Asked an interview question ,async await How to achieve concurrency ？ I suddenly remembered tonight , Hurry up and tidy up .

give an example

var fs=require('fs');
var read=function (path) {
    
    return new Promise((resolve,reject)=>{
    
            fs.readFile(path,(err,data)=>{
    
                if(err){
    
                    reject(err)
                }else{
    
                    resolve(data)
                }
            })
    })
}
// Secondary read 
async function ReadTwo(){
    
    var f1=await read('./a.txt');
    var f2=await read('./b.txt');
}

Solution

(1) promise.all()

async function readTwo{
    
	var p=Promise.all([read('./a.txt'),read('./b.txt')]);
	var [f1,f2]=await p
}

because promise.all It's concurrency , So these two requests are really concurrent

(2) Can't describe , Look at the code

async function readTwo{
    
	var p1=read('./a.txt');
	var p2=read('./a.txt');
	f1=await p1;
	f2=await p2;
}

These two requests are really concurrent , Because they are asynchronous functions , However, the assignment after obtaining the result is secondary

It's easy to think about it now , Not at that time .