javascript - Promise 的串行执行

Question

我想执行一个带有从值数组循环的参数的函数。每次执行都必须等待前一个执行完成。下面的示例代码应打印:

Done: 1
Done: 2
Done: 3
Done: 4
Done: 5

谢谢!

页

'use strict';

function f1(value) {
    return new Promise((resolve, reject) => {
        setTimeout(function() {
            console.log('Done: ' + value);
            resolve(true)
        }, Math.random() * 2000 + 1000);
    });
}

const vs = [0,1,2,3,4,5];

vs.reduce((start, next) => {
    return f1(next)
})

Answer 1

如果你只想要 ES6，试试这个:

'use strict';

function f1(value) {
    return new Promise((resolve, reject) => {
        setTimeout(function() {
            console.log('Done: ' + value);
            resolve(true)
        }, Math.random() * 2000 + 1000);
    });
}

const vs = [0,1,2,3,4,5];

let promiseChain = vs.reduce((start, next) => {
    return start.then(() => f1(next));
}, Promise.resolve());

promiseChain.then(() => console.log('Done!'));

如果您有兴趣从分辨率中获取值，可以尝试 this也是如此。