Utilize jQuery in phantom.js to send an ajax request across domains

I am currently in the process of testing a chrome plugin by emulating a portion of its functionality on phantomjs.

My objective for phantom seems quite straightforward, yet I am encountering issues. I aim for it to navigate to a specific webpage and within that page's context, execute a script that will send an ajax request to my backend and display the response. To simplify matters, I prefer phantom to utilize jQuery for ajax requests.

Below is the script test1.js that I am providing to phantom:

var page = new WebPage(),
    url = 'http://www.example.com',

// Callback is executed each time a page is loaded...
page.open(url, function (status) {
  if (status === 'success') {
    console.log('opened url');
    start();
  }
});

function start(){
  page.includeJs('https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js', function() {
    console.log("got here");
    $.get("http://my-wonderful-site.com")
      .done(function( data ) {
        console.log("here!");
        console.log(data);
        phantom.exit(); 
      });
  });
}

The output in the console when running the command

phantomjs test1.js --web-security=false
is as follows:

opened url
got here
ReferenceError: Can't find variable: $

  test1.js:20
  :/modules/webpage.js:337

It appears that even jQuery fails to load, and I am unable to determine my mistake. I attempted using page.injectJs to inject jQuery from my local drive, yet encountered the same error. Could you offer assistance?

Edited:

Following the suggested advice, I updated the function:

function start(){
  page.includeJs('https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js', function() {
    console.log("got here");
    page.evaluate(function() {
      console.log("and here");
      $.get("http://my-wonderful-site.com")
        .done(function( data ) {
          console.log("here!");
          console.log(data);
          phantom.exit(); 
        });
    });
  });
}

Now, phantom simply hangs, and the console output displays:

phantomjs test1.js --web-security=false
opened url
got here

Specifically, the console.log statement right before the $.get call does not execute at all.

Answer №1

PhantomJS operates with two distinct contexts. The inner context, known as the page context, is isolated and cannot access variables from the outer scope. This means it does not recognize objects like phantom. Similarly, the outer context is unaware of elements such as $ because jQuery is injected into the page separately. To interact with jQuery within PhantomJS, you must encapsulate your requests in page.evaluate().

Furthermore, calling phantom.exit() directly will not suffice due to the asynchronous nature of the process. Instead, utilize a combination of page.onCallback and window.callPhantom() to initiate the exit sequence from within the page context.

page.onCallback = function(data){
  if (data.type === "exit") {
    phantom.exit();
  }
};

function start(){
  page.includeJs('https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js', function() {
    console.log("got here");
    page.evaluate(function(){
      $.get("http://my-wonderful-site.com")
        .done(function( data ) {
          console.log("here!");
          console.log(data);
          window.callPhantom({type: "exit"});
        });
    });
  });
}

Although console.log() is available within the page context, its output is not displayed by default. To view these messages, you need to register for the page.onConsoleMessage event.

To exchange data between contexts, consider using callPhantom() instead of logging information. Remember that only simple primitive objects can be shared between the contexts:

Note: The arguments and the return value exchanged via the evaluate function must be basic primitive types. If it can be serialized through JSON, it is suitable for transfer.

Closures, functions, DOM nodes, etc. are not compatible!

In addition, make use of event handlers like onError, onResourceError, and onResourceTimeout to troubleshoot any potential issues that may arise.

Answer №2

It is necessary to be within a page.evaluate in order to effectively utilize the injected JS (check out this example here http://phantomjs.org/page-automation.html). You can try the following code snippet:

function start() {
    page.includeJs('https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js', function() {
        console.log("successfully loaded jQuery");
        page.evaluate(function() {
            $.get("http://my-wonderful-site.com")
            .done(function( data ) {
              console.log("Success!");
              console.log(data);
              phantom.exit(); 
            });
        });
    });
}

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