koa2

promise对象的使用

let state = 1;

function step1(resolve, reject) {
    console.log('1.洗菜');
    if(state == 1) {
        resolve('洗菜完成');
    } else {
        reject('洗菜错误');
    }
}

function step2(resolve, reject) {
    console.log('2.吃饭');
    if(state == 1) {
        resolve('吃饭完成');
    } else {
        reject('吃饭错误');
    }
}

function step3(resolve, reject) {
    console.log('3.洗碗');
    if(state == 1) {
        resolve('洗碗完成');
    } else {
        reject('洗碗错误');
    }
}

new Promise(step1).then(function(val) {    //new promise(step1).then().then().then()
    console.log(val);
    return new Promise(step2);
}).then(function(val) {
    console.log(val);
    return new Promise(step3);
}).then(function(val) {
    console.log(val);
})

　　

const Koa = require('koa')
const app = new Koa()
 
app.use( async ( ctx ) => {
  ctx.body = 'hello koa2'
})
 
app.listen(3000)
console.log('[demo] start-quick is starting at port 3000')