js继发并发

(async () => {
    const delays = [1,2,3,4,5];
    while(delays.length > 0){
        const delay = delays.shift();
        console.log(`Start delay: ${delay} loop`)
        await new Promise((resolve) => {
            setTimeout(()=>{
                resolve();
            },delay * 1000)
        })
        console.log(`\End delay: ${delay} loop\n`)
    }
})()

 

 

async function aaa(){
  let a = await some1()
  let b = await some2()
//这样的写法是继发的 相当于A执行完毕后再执行B
}
async function aaa(){
  let a = some1()
  let b = some2()
  let aDone = await a
  let bDone = await b
//这样的写法是并发的 无先后顺序
}

// 并发的两种写法
// 写法一
let [foo, bar] = await Promise.all([getFoo(), getBar()]);

// 写法二
let fooPromise = getFoo();
let barPromise = getBar();
let foo = await fooPromise;
let bar = await barPromise;