使用async和await来避免进入回调地狱的示例

使用async和await来避免进入回调地狱的示例

const fs = require('fs')
const util = require('util')

const read = util.promisify(fs.readFile)

async function run(){
    try {
        let data = await read('logger.js','utf-8')
        console.log(data)
    } catch(e) {
        console.log(e)
    }
}
run()

async 和 await 同样可以作用在promise.all上

//index.js
fs = require('fs')
util = require('util')

var read = util.promisify(fs.readFile)
var run = async () => {
    var data = await Promise.all([
        read('logger.js'),
        read('logger.js'),
        read('logger.js')
        ]
    )
    console.log(data[0].toString())
}
run()
// logger.js 和 index.js 放置在同一目录下

其他的示例

async function run(){
    setTimeout(() => {
        console.log('1 sec after')
    }, 1000);
    console.log('start')
    await sleep(3)
    console.log('end')
}
async function sleep(sec) {
    return  new Promise((resolve, reject) => {
        setTimeout(()=>{
            console.log('after ', sec , 'secs')
            resolve(1)
        }, sec * 1000)
    })
}
run();

有关nodejs中代码执行顺序的讲解