Monkey patch jquery
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So what exactly we have done here is, we can see additional logging with its normal working. This was done in order to focus on the techniques of MP. With a plus account, you get your own tailored art sharing network. But if wielding that power doesn't scare and humble you a little, too, then maybe you should leave the monkeypatching to the. Typically you should strive to apply your changes as close as possible to the target, but keep in mind that the implementation of the target might change over time.
This article was peer reviewed by and. Have you ever worked with third-party code that worked well except for one little thing that drove you nuts? Why did the creator forget to remove those pesky console logs? If so then you know it can be difficult or impossible to get your changes implemented by the maintainer. But what about changing the code yourself? Welcome to a journey into the world of Monkey Patching in JavaScript! What is Monkey Patching? This is done by replacing the original behavior with a fixed version. This article will use an existing which displays a simple, slide-able Popup, as seen in the figure below, containing a feedback form. The source code was modified to include use-cases which act as the MP targets. By target I mean a specific piece of functionality, feature or, at the lowest level, method which we are going to patch. Another modification I made was to remove the immediately invoked function expression IIFE surrounding the code. This was done in order to focus on the techniques of MP. You can find the whole example, including the monkey patches discussed in this article,. But as always, there are different tools and techniques available which vary in their suitability for certain scenarios. What seems extreme, crazy, or simply bad sometimes may be the last resort for a specific case. The situation described here might be an unnatural one, driven to the extreme with a fake widget, to show what your options are. You, as the reader, then have to decide whether you like what you see or not. If nothing else, after reading this you will have a better understanding in order to argue against MP. Hardcoded background color The first of them is a method called toggleError which is supposed to change the background color of an element based on a boolean parameter FeedbackBox. Pesky console logs While developing the widget, a console log was used give the dev hints about what currently is executing. What might be a nice approach during development, for sure is not the nicest thing to do in a production use. As such we need to find a way to strip all those debug statements. Intercepting ad-server calls The widget is great, but it has one strange behavior. Each time you initialize the script, it will make a request to a strange ad server and display unnecessary bloat on our page. NOTE: The demo code targets a JSON file inside the Plunker to simulate an outgoing Ajax request, but I hope you get the point. Overwriting a Method One of the key concepts of MP is to take an existing function and augment it with custom behavior before or after the call to the original code. But calling the original implementation is not always necessary as sometimes you just want to replace it with your custom actions. This approach is ideal to help us to solve the hardcoded background color. The location where you apply your MP needs to be after the original implementation is loaded and available. Typically you should strive to apply your changes as close as possible to the target, but keep in mind that the implementation of the target might change over time. As for our example, the initialization along with the MPs will go into the file main. Looking at the widget implementation, we can see there is a FeedbackBox object which serves as the widgets root. } Since JavaScript is a dynamic language and its objects can be modified at runtime, what we ultimately will do is simply replace toggleError with our custom method. The only thing to remember is to keep the signature the name and passed arguments the same. Augmenting a Method In the previous example, we saw how to overwrite the original implementation by providing our own. Taking care of the console logs on the other hand is supposed to essentially only filter out specific calls and suppress them. Typically this is done by firing up the developer console in your browser of choice and peek into the loaded resources, add break points and debug target code parts to get a feel for what it does. This time, though, all you need to do is open up the implementation from the Plunker example called in another tab. By looking at the debug messages we can see that each one of them starts with FeedbackBox:. So an easy way to achieve what we want is to intercept the original call, inspect the provided text to be written and call the original method only if it does not contain the debug hint. In order to do so lets first store the original console. Then we again override the original one with our custom implementation, which first checks whether the provided attribute text is of type string and if so, whether it contains the substring FeedbackBox:. Note that this method takes the context as first parameter, that means the object on which the method should be called, and a magical arguments variable. The later is an array of all the arguments originally passed in to the original console log call. So instead of defining all of them, which can be quite hard for endless possibilities, we simply forward all whats coming there. Depending on how good your search skills are you may or may not find a suitable answer. But lets stop for a moment and think about what actually happens here. No matter what jQuery does with its ajax method, at some time it will eventually create a native XMLHttpRequest. So the idea is to monkey patch the send method and tell it not to execute calls to a specific URL. So what do we do? We make it available on the object. Looking for the first chance to get hold of the URL, we can see the open method accepts it as the second parameter. As before, we will store the original open method in a variable for later use. We then overwrite the original with our custom implementation. But, more than that, I hope the article was able to give you an idea how you should approach a problem with monkey patches. He is passionate about developing Single Page Applications, grinding LOB Apps with. NET and is pushing more and more towards Node. Moreover, he is hopelessly in love with the Durandal Framework and, while still using other libraries in his day job, he's working hard contributing as a core team member as much as possible to Aurelia.
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