如何在不使用第三方库的情况下使用Node.js下载文件?

我不需要什么特别的东西。我只想从给定的URL下载文件,然后将其保存到给定的目录。


当前回答

说到处理错误,监听请求错误甚至更好。我甚至会通过检查响应代码来验证。这里认为只有200个响应代码成功,但其他代码可能很好。

const fs = require('fs');
const http = require('http');

const download = (url, dest, cb) => {
    const file = fs.createWriteStream(dest);

    const request = http.get(url, (response) => {
        // check if response is success
        if (response.statusCode !== 200) {
            return cb('Response status was ' + response.statusCode);
        }

        response.pipe(file);
    });

    // close() is async, call cb after close completes
    file.on('finish', () => file.close(cb));

    // check for request error too
    request.on('error', (err) => {
        fs.unlink(dest, () => cb(err.message)); // delete the (partial) file and then return the error
    });

    file.on('error', (err) => { // Handle errors
        fs.unlink(dest, () => cb(err.message)); // delete the (partial) file and then return the error
    });
};

尽管这段代码相对简单,但我建议使用request模块,因为它处理更多http不支持的协议(你好,HTTPS!)。

可以这样做:

const fs = require('fs');
const request = require('request');

const download = (url, dest, cb) => {
    const file = fs.createWriteStream(dest);
    const sendReq = request.get(url);
    
    // verify response code
    sendReq.on('response', (response) => {
        if (response.statusCode !== 200) {
            return cb('Response status was ' + response.statusCode);
        }

        sendReq.pipe(file);
    });

    // close() is async, call cb after close completes
    file.on('finish', () => file.close(cb));

    // check for request errors
    sendReq.on('error', (err) => {
        fs.unlink(dest, () => cb(err.message)); // delete the (partial) file and then return the error
    });

    file.on('error', (err) => { // Handle errors
        fs.unlink(dest, () => cb(err.message)); // delete the (partial) file and then return the error
    });
};

编辑:

要使它与https兼容,请更改

const http = require('http');

to

const http = require('https');

其他回答

如果您正在使用express,请使用res.download()方法。否则使用fs模块。

app.get('/read-android', function(req, res) {
   var file = "/home/sony/Documents/docs/Android.apk";
    res.download(file) 
}); 

(or)

   function readApp(req,res) {
      var file = req.fileName,
          filePath = "/home/sony/Documents/docs/";
      fs.exists(filePath, function(exists){
          if (exists) {     
            res.writeHead(200, {
              "Content-Type": "application/octet-stream",
              "Content-Disposition" : "attachment; filename=" + file});
            fs.createReadStream(filePath + file).pipe(res);
          } else {
            res.writeHead(400, {"Content-Type": "text/plain"});
            res.end("ERROR File does NOT Exists.ipa");
          }
        });  
    }

您可以创建一个HTTP GET请求,并将其响应管道到可写文件流:

const http = require('http'); // or 'https' for https:// URLs
const fs = require('fs');

const file = fs.createWriteStream("file.jpg");
const request = http.get("http://i3.ytimg.com/vi/J---aiyznGQ/mqdefault.jpg", function(response) {
   response.pipe(file);

   // after download completed close filestream
   file.on("finish", () => {
       file.close();
       console.log("Download Completed");
   });
});

如果您希望支持在命令行上收集信息(比如指定目标文件或目录或URL),可以使用类似Commander的工具。

更详细的解释在https://sebhastian.com/nodejs-download-file/

Gfxmonk的答案在回调和file.close()完成之间有一个非常紧张的数据竞赛。File.close()实际上接受一个回调函数,该函数在close完成时被调用。否则,立即使用文件可能会失败(非常罕见!)。

一个完整的解决方案是:

var http = require('http');
var fs = require('fs');

var download = function(url, dest, cb) {
  var file = fs.createWriteStream(dest);
  var request = http.get(url, function(response) {
    response.pipe(file);
    file.on('finish', function() {
      file.close(cb);  // close() is async, call cb after close completes.
    });
  });
}

如果不等待finish事件,幼稚的脚本可能最终得到一个不完整的文件。如果不通过close调度cb回调,您可能会在访问文件和文件实际准备就绪之间出现竞争。

对于那些寻找es6风格的基于承诺的方式的人来说,我猜它会是这样的:

var http = require('http');
var fs = require('fs');

function pDownload(url, dest){
  var file = fs.createWriteStream(dest);
  return new Promise((resolve, reject) => {
    var responseSent = false; // flag to make sure that response is sent only once.
    http.get(url, response => {
      response.pipe(file);
      file.on('finish', () =>{
        file.close(() => {
          if(responseSent)  return;
          responseSent = true;
          resolve();
        });
      });
    }).on('error', err => {
        if(responseSent)  return;
        responseSent = true;
        reject(err);
    });
  });
}

//example
pDownload(url, fileLocation)
  .then( ()=> console.log('downloaded file no issues...'))
  .catch( e => console.error('error while downloading', e));

不要忘记处理错误!下面的代码是基于Augusto Roman的回答。

var http = require('http');
var fs = require('fs');

var download = function(url, dest, cb) {
  var file = fs.createWriteStream(dest);
  var request = http.get(url, function(response) {
    response.pipe(file);
    file.on('finish', function() {
      file.close(cb);  // close() is async, call cb after close completes.
    });
  }).on('error', function(err) { // Handle errors
    fs.unlink(dest); // Delete the file async. (But we don't check the result)
    if (cb) cb(err.message);
  });
};