Check for function called

Question

Just wondering if there is anyway to fire some code when a function is called, without adding the code to the function, for example:

function doSomething(){
    //Do something
}

//Code to call when doSomething is called

Answer 1

You can wrap the function :

(function(){
   var oldFunction = doSomething;
   doSomething = function(){
       // do something else
       oldFunction.apply(this, arguments);
   }
})();

I use an IIFE here just to avoid polluting the global namespace, it's accessory.