Enhancing the functionality of XMLHttpRequest.open()

Question

Enhancing the functionality of XMLHttpRequest.open()

How can I intercept and modify the arguments of the XMLHttpRequest.open() method?

I attempted using the proxy method, but it was unsuccessful. I removed the override when XMLHttpRequest() was called:

(function() {
    var intercepted = window.XMLHttpRequest.open;
    window.XMLHttpRequest.open = function() {
        $('.log').html(arguments[0]);
        return intercepted.apply(this, arguments);
    };
})();

javascript ajax xmlhttprequest overriding

Answer 1

Answer №1

Instead of changing the open method that is inherited by XMLHttpRequest objects, you are simply adding a method to the XMLHttpRequest constructor that is never actually utilized.

I tested this piece of code on Facebook and was successful in capturing the requests:

(function() {
    var proxied = window.XMLHttpRequest.prototype.open;
    window.XMLHttpRequest.prototype.open = function() {
        console.log( arguments );
        return proxied.apply(this, [].slice.call(arguments));
    };
})();

/*
    ["POST", "/ajax/chat/buddy_list.php?__a=1", true]
    ["POST", "/ajax/apps/usage_update.php?__a=1", true]
    ["POST", "/ajax/chat/buddy_list.php?__a=1", true]
    ["POST", "/ajax/canvas_ticker.php?__a=1", true]
    ["POST", "/ajax/canvas_ticker.php?__a=1", true]
    ["POST", "/ajax/chat/buddy_list.php?__a=1", true]
*/

To clarify, the open method should be added to the XMLHttpRequest prototype (window.XMLHttpRequest.prototype) rather than the XMLHttpRequest constructor (window.XMLHttpRequest).

Answer 2

Instead of changing the open method that is inherited by XMLHttpRequest objects, you are simply adding a method to the XMLHttpRequest constructor that is never actually utilized.

I tested this piece of code on Facebook and was successful in capturing the requests:

(function() {
    var proxied = window.XMLHttpRequest.prototype.open;
    window.XMLHttpRequest.prototype.open = function() {
        console.log( arguments );
        return proxied.apply(this, [].slice.call(arguments));
    };
})();

/*
    ["POST", "/ajax/chat/buddy_list.php?__a=1", true]
    ["POST", "/ajax/apps/usage_update.php?__a=1", true]
    ["POST", "/ajax/chat/buddy_list.php?__a=1", true]
    ["POST", "/ajax/canvas_ticker.php?__a=1", true]
    ["POST", "/ajax/canvas_ticker.php?__a=1", true]
    ["POST", "/ajax/chat/buddy_list.php?__a=1", true]
*/

To clarify, the open method should be added to the XMLHttpRequest prototype (window.XMLHttpRequest.prototype) rather than the XMLHttpRequest constructor (window.XMLHttpRequest).

Answer 3

Answer №2

When it comes to mastering the dark arts of XHR monkey patching, one approach I find effective is enclosing everything in an IIFE. This sets the stage for overriding methods in a clean and organized manner.

First, wrap your code in an IIFE like this:

(function(open, send) {
    //...overrides of the XHR open and send methods are now encapsulated within a closure
})(XMLHttpRequest.prototype.open, XMLHttpRequest.prototype.send)

Following this structure allows you to easily modify both the open and send methods of XMLHttpRequest. By passing in the base methods as arguments to the IIFE, you can safely manipulate them within the function block.

To persist your changes, you'll need to replicate the method signatures, apply your modifications, and assign them to the XHR prototype property. This ensures all XHR requests will go through your code.

For example, the "open" method can be modified like this:

XMLHttpRequest.prototype.open = function(method, url, async, user, password) {
      xhrOpenRequestUrl = url;     // update request url, closure variable
      open.apply(this, arguments); // reset/reapply original open method
};

Similarly, the "send" method can be altered to suit your needs:

XMLHttpRequest.prototype.send = function(data) {
  //...any additional code you require
  if (this.readyState == 4 && this.status >= 200 && this.status < 300) {
    xhrSendResponseUrl = this.responseURL;
    responseData = this.data;  // now you have access to the data
  }
  send.apply(this, arguments); // reset/reapply original send method
}

Remember to use the "apply" method to finalize your changes after all overrides have been implemented. By organizing your modifications within an IIFE, you can prevent potential conflicts with other scripts that may be altering XHR behavior.

Overall, this structured approach to XHR monkey patching can be a powerful tool in your development arsenal. Just be mindful of the order in which your scripts are loaded to avoid unexpected conflicts. Happy patching!

Answer 4

When it comes to mastering the dark arts of XHR monkey patching, one approach I find effective is enclosing everything in an IIFE. This sets the stage for overriding methods in a clean and organized manner.

First, wrap your code in an IIFE like this:

(function(open, send) {
    //...overrides of the XHR open and send methods are now encapsulated within a closure
})(XMLHttpRequest.prototype.open, XMLHttpRequest.prototype.send)

Following this structure allows you to easily modify both the open and send methods of XMLHttpRequest. By passing in the base methods as arguments to the IIFE, you can safely manipulate them within the function block.

To persist your changes, you'll need to replicate the method signatures, apply your modifications, and assign them to the XHR prototype property. This ensures all XHR requests will go through your code.

For example, the "open" method can be modified like this:

XMLHttpRequest.prototype.open = function(method, url, async, user, password) {
      xhrOpenRequestUrl = url;     // update request url, closure variable
      open.apply(this, arguments); // reset/reapply original open method
};

Similarly, the "send" method can be altered to suit your needs:

XMLHttpRequest.prototype.send = function(data) {
  //...any additional code you require
  if (this.readyState == 4 && this.status >= 200 && this.status < 300) {
    xhrSendResponseUrl = this.responseURL;
    responseData = this.data;  // now you have access to the data
  }
  send.apply(this, arguments); // reset/reapply original send method
}

Remember to use the "apply" method to finalize your changes after all overrides have been implemented. By organizing your modifications within an IIFE, you can prevent potential conflicts with other scripts that may be altering XHR behavior.

Overall, this structured approach to XHR monkey patching can be a powerful tool in your development arsenal. Just be mindful of the order in which your scripts are loaded to avoid unexpected conflicts. Happy patching!

Answer 5

Answer №3

For a great illustration of effectively overriding the XMLHttpRequest object, I highly recommend exploring the xmlhttprequest project on google code. It serves as a solid example of how to do it right. The complete source code is available for viewing here.

Answer 6

For a great illustration of effectively overriding the XMLHttpRequest object, I highly recommend exploring the xmlhttprequest project on google code. It serves as a solid example of how to do it right. The complete source code is available for viewing here.

Answer 7

Answer №4

Try utilizing the XMLHttpRequest.prototype.open method instead.

Answer 8

Try utilizing the XMLHttpRequest.prototype.open method instead.

Enhancing the functionality of XMLHttpRequest.open()

Answer №1

Answer №2

Answer №3

Answer №4

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