node.js - 等到顺序 promise 解决后再在 Node 中继续

Question

我正在尝试使用“reduce”设置顺序解析，然后继续做一些其他工作，但它似乎没有等待，它只是继续。如何等待数组中的每个 Promise 完成？

function Work(data){
    return new Promise((resolve)=>{resolve()});
}
function DoWork(data){
    return new Promise((resolve, reject)=>{
        setTimeout(() => {
            Work(data)
                .then(() => {
                    console.log("Doing work on '"+data+"'");
                    resolve();
                })
                .catch(err => {
                    console.log("Failed to do work on '"+data+"'");
                    reject(err);
                });
        }, 1000);
    });
}
var AllMyWork= ["a","b","c"];
AllMyWork.reduce((p, data) => p.then(DoWork(data)), Promise.resolve())
.then(result => {
    console.log("All work is finished");
})
.catch(err => {
    console.log("MyArray reduce has failed");
});

这是我得到的回复:

All work is finished
Doing work on 'a'
Doing work on 'b'
Doing work on 'c'

我想做的是等到所有工作完成然后写入消息“所有工作已完成”。

Answer 1

p.then(DoWork(data))

这会立即调用DoWork。您想要将函数传递给 .then:

p.then(() => DoWork(data))

减少其他方面都很好。示例:

delay = ms => new Promise(resolve => setTimeout(resolve, ms));

DoWork = work => delay(1000).then(() => console.log("did work", work));

AllMyWork = ["a","b","c"];
AllMyWork.reduce((p, data) => p.then(() => DoWork(data)), Promise.resolve())
.then(result => {
    console.log("All work is finished");
});