使用噩梦下载文件 [英] Download a file using Nightmare

问题描述

我正在使用噩梦来为今天的报纸创建一个自动下载器。我设法登录并进入指定的页面。但是我无法找到如何使用噩梦下载文件。

I am using Nightmare to create a automated downloader for today's newspaper. I managed to login and go the the specified page. However I could not find out how to download a file with Nightmare.

var Nightmare = require('nightmare');
new Nightmare()
  .goto('https://login.nrc.nl/login?service=http://digitaleeditie.nrc.nl/welkom')
    .type('input[name="username"]', 'Username')
    .type('input[name="password"]','Password')
    .click('button[type="submit"]')
    .wait()
    .goto('http://digitaleeditie.nrc.nl/digitaleeditie/NH/2014/10/20141124___/downloads.html')
    .wait()
    .click('a[href="/digitaleeditie/helekrant/epub/nrc_20141124.epub"]')
    .wait()

    .url(function(url) {
        console.log(url)
    })
    .run(function (err, nightmare) {
      if (err) return console.log(err);
      console.log('Done!');
    });

我尝试通过点击下载按钮下载文件。但是这似乎不起作用。

I tried to download the file by clicking on the download button. However this seems not to work.

推荐答案

PhantomJS（和CasperJS和Nightmare）不会触发下载（对话框）点击应该下载的东西。所以，有必要自己下载。如果您可以找到文件的URL，那么可以使用XMLHttpRequest从页面上下文轻松下载。

PhantomJS (and CasperJS and Nightmare) don't trigger a download (dialog) when you click on something that should be downloaded. So, it is necessary to download it yourself. If you can find out the URL of the file, then it can be easily downloaded using an XMLHttpRequest from the page context.

所以你需要交换

.click('a[href="/digitaleeditie/helekrant/epub/nrc_20141124.epub"]')

for

.evaluate(function ev(){
    var el = document.querySelector("[href*='nrc_20141124.epub']");
    var xhr = new XMLHttpRequest();
    xhr.open("GET", el.href, false);
    xhr.overrideMimeType("text/plain; charset=x-user-defined");
    xhr.send();
    return xhr.responseText;
}, function cb(data){
    var fs = require("fs");
    fs.writeFileSync("book.epub", data, "binary");
})

您还可以使用更新的请求二进制数据的方式。

You can also use the newer way of requesting binary data.

.evaluate(function ev(){
    var el = document.querySelector("[href*='.pdf']");
    var xhr = new XMLHttpRequest();
    xhr.open("GET", el.href, false);
    xhr.responseType = "arraybuffer";
    xhr.send();

    var bytes = [];
    var array = new Uint8Array(xhr.response);
    for (var i = 0; i < array.length; i++) {
        bytes[i] = array[i];
    }
    return bytes;
}, function cb(data){
    var fs = require("fs");
    fs.writeFileSync("book.epub", new Buffer(data), "binary");
})

这两种方式都被描述 。 这里是一个示例脚本，显示了一个概念证明。

Both of the ways are described on MDN. Here is a sample script which shows a proof of concept.

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