Override JavaScript functions

It‘s very easy to override functions in JavaScript. You simply assign another function to the function name.

var myFunction = function () {
    // do something...
myFunction = function () {
    // do something different...

But it’s also possible to extend the existing function in order to execute something before or after the existing function.

myFunction = (function () {
    var oldMyFunction = myFunction;
    return function () {
        // do something before...
        oldMyFunction.apply(this, arguments);
        // ...and after

The new variable oldMyFunction is required as the function would call itself over and over again otherwise. By using apply() and the arguments array, you don’t have to worry about the parameters as all passed parameters will be looped through.

This code definitely won’t win any beauty contests and may not be simple to understand, but may be useful for extending module code.