Question

我有这段代码：

var urls = ["url1","url2","url3"];
urls.forEach(function(url,i) {
promiseFunction(url)
}

function promiseFunction(string) {
    return new Promise(function(resolve, reject) {
        //Fetch
        //Compute
        resolve()
    });
}

所以我想迭代一个url数组，对于每个url，我想调用使用Bluebird promise库进行一些获取和计算的promiseFunction，我的问题是如何在继续迭代之前等待promise的响应下一个元素？我有Node JS 6.10.0，目前我无法切换版本，所以我不能使用async / await API。有人可以帮帮我吗？

在Svenskunganka回应之后，我用他的回答更新了我的问题：

var urls = [{name:"url1", delay: 1000},{name:"url2", delay: 5000},{name:"url3", delay: 3000}];

Promise.all(urls.map(promiseFunction)).then((results) => {
    console.log(results)
  }).catch((e) => {
    // Handle the error
  })

function promiseFunction(url) {
    return new Promise(function(resolve, reject) {
        console.log("Started "+url.name)
        setTimeout(
            function(){
                console.log(url.name+ " delay: "+url.delay)
                resolve(url.delay) 
        }, url.delay);
    });
}

如果您测试它，您可以立即看到该打印：开始url1 开始url2 开始url3

所以不等，我认为答案不正确或者我不明白

有人已经关闭了这个问题，因为它被认为是重复的，与链接为重复的问题不同，无论如何我找到了解决我的问题的方法，如果有人需要：

var Promise = require("bluebird");

var urls = [{name:"url1", delay: 5000},{name:"url2", delay: 1000},{name:"url3", delay: 3000}];

var a = () => promiseFunction(urls[0]);
var b = () => promiseFunction(urls[1]);

function promiseFunction(url) {
    return new Promise(function(resolve, reject) {
        console.log("Started "+url.name)
        setTimeout(
            function(){
                console.log(url.name+ " delay: "+url.delay)
                resolve(url.delay) 
        }, url.delay);
    });
}

Promise.map([a, b], function (promiseFn) {
    return promiseFn(); //make sure that here You return Promise
}, {concurrency: 1}); //it will run promises sequentially

如何在forEach中等待每次迭代调用Promise函数

0 个答案: