Question

以下内容有效，但似乎我缺少了一点数据。实现我在这里想要做的最好的方法是什么。我运行node updateFiles.js 5.5.9，闪电般快，但是就像我说的那样，当我盯着结果文件时，似乎错过了一些块……？

下面是updateFiles.js的内容。

const fs = require('fs');
const fetch = require('node-fetch');
var version = process.argv[2];
var filePath = 'source/js/firebase.js';
var sdks = [
'https://www.gstatic.com/firebasejs/' + version + '/firebase-app.js',
'https://www.gstatic.com/firebasejs/' + version + '/firebase-auth.js',
'https://www.gstatic.com/firebasejs/' + version + '/firebase-database.js',
'https://www.gstatic.com/firebasejs/' + version + '/firebase-firestore.js',
'https://www.gstatic.com/firebasejs/' + version + '/firebase-messaging.js',
'https://www.gstatic.com/firebasejs/' + version + '/firebase-functions.js'
]; 

//fetch each firebase file and write it to source/js/firebase.js
for (var sdk of sdks){
    fetch(sdk).then(res => {
        const dest = fs.createWriteStream(filePath,{flags:'a'});
        res.body.pipe(dest);
    });    
}

更新：我最终这样做了，而且似乎可行，但是，如果那里有一个专家可以指出更好的方法，请告诉我。预先谢谢你。

const fs = require('fs');
const fetch = require('node-fetch');
var version = process.argv[2];
var promisesArray = [];
var sdks = [
// Firebase App is always required and must be first
'https://www.gstatic.com/firebasejs/' + version + '/firebase-app.js',
// Add additional services that you want to use
'https://www.gstatic.com/firebasejs/' + version + '/firebase-auth.js',
'https://www.gstatic.com/firebasejs/' + version + '/firebase-database.js',
'https://www.gstatic.com/firebasejs/' + version + '/firebase-firestore.js',
'https://www.gstatic.com/firebasejs/' + version + '/firebase-messaging.js',
'https://www.gstatic.com/firebasejs/' + version + '/firebase-functions.js'
];

var filePath = 'source/js/firebase.js'; 

for (var sdk of sdks){
    promisesArray.push(fetch(sdk));
}

Promise.all(promisesArray).then(sdkFiles => {
    for (var file of sdkFiles){
        const dest = fs.createWriteStream(filePath,{flags:'a'});
        file.body.pipe(dest);
    }
});

Answer 1

也许您不能一次写入所有文件，而是等待每个文件被处理然后继续处理另一个文件？来自循环的承诺来自：JavaScript ES6 promise for loop

for (let i = 0, p = Promise.resolve(); i < sdks.length; i++) {
  p = p.then(_ => new Promise(resolve =>
    fetch(sdks[i]).then(res => {
      const dest = fs.createWriteStream(filePath, { flags: 'a' });
      res.body.pipe(dest);
      resolve()
    })
  ));
}

Node.js获取远程文件并在本地连接和保存它们

1 个答案: