nightmare.js-$未定义

Question

I want to use jquery in my web scraping with nightmare.js . Based on this tutorial , I can just inject the jquery and copy the file to the same root folder. But somehow I still get error:

ReferenceError: $ is not defined

Below is my code:

var Nightmare = require('nightmare');

new Nightmare()
  .goto('http://google.com')
  .inject('js', 'jquery.min.js')
  .wait()
  .run(function(err, nightmare) {
    if (err) {
      console.log(err);
    };

    var items = [];

    $('.someclass').each(function(){//<-- error - $ not defined
        item = {};
        item.value = $(this).val();
        items.push(item);
    });
    console.log(items);
    });

Answer 1

To be able to interact with the page and its variables, you'll need to use .evaluate(fn) :

Invokes fn on the page with arg1, arg2,... .

.evaluate() changes the context of the fn to that of the page, so that it can be execute as though it's client-side code, with access to the window , document , $ , and any other globals.

Also, since you've mentioned using version 2.10, the .run() function from 1.x versions has been replaced by Promise s , so you'll want to use .then() and .catch() to handle successes and errors, respectively.

For your snippet:

new Nightmare()
  .goto('http://google.com')
  .inject('js', 'jquery.min.js')
  .wait()
  .evaluate(function() {
    var items = [];

    $('.someclass').each(function(){
        item = {};
        item.value = $(this).val();
        items.push(item);
    });

    console.log(items);
  })
  .then(function () {
    console.log('Done');
  });
  .catch(function (err) {
    console.log('Error', err);
  });

The project's readme includes a few examples of this method chain .