Beware of Javascript frameworks extending the Array

Apr 23, 2013 javascript

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MooTools, a common Javascript framework, is responsible for extending an array in Javascript. It adds a number of useful features to each array that is created.

However, this can be a problem. When creating a third-party javascript widget, I created an array of properties that needed to be iterated through. I obviously cannot depend on a specific Javascript framework to be present… so I did something like this:

for (x in myArray) {
  doSomethingWith(myArray[x]);
}

Well, since each array - on creation - has the methods from the prototype being extended, I now have extra items in my array. This was causing an error because my function was not expecting a function to be passed in, only a string.

So that’s why this is bad. So don’t do that in Javascript, ok? Thanks! :)