Append code to the end of an existing function

Question

I need to trigger function bar() whenever function foo() fires. I have no control over function foo or whether it will change in the future. I have this situation regularly (and

Answer 1

function extend(fn,code){
  return function(){
    fn.apply(fn,arguments)
    code.apply(fn,argumnets)
  }
}

and use it like this:

function appendToFunction(fn,code){ 
    if(typeof fn == 'function'){
        var fnCode = fn.toString() ;
        fnCode = fnCode.replace(/\}$/,code+"\n}") ;
        window.eval(fnCode);                    // Global scope
        return true ;
    }
    else{
        return false ;
    }
}

appendToFunction = extend(appendToFunction,function(){/*some code*/});

this will give you the same "this" in both functions