Question

i need to “detect” when some third party function returns and then execute my own function.

example: some function i didn’t write

function foo(params1){
  console.log(params1);
}

my function:

function bar(params2){
  console.log(params2);
}

i need that whenever foo is called, it somehow calls bar immediately !
i tried going this way:

foo = function(params1){
  console.log(params1);
  bar(params2);
}

meaning i “overwrite” foo .. but sometimes (always), foo code is too lengthy + passing params2 (minor) problem.
I tried desperate attempts with prototype and so .. but then i figured i need some support on this.

i also tried this: (but)

var tmp = foo;
foo = function(params1) {
  tmp(params1);
  bar(params2);
}

Same problem here, the caller will call foo(params1) thus bar won’t “find” params2.

---

I need this to make something like an “event handler”.
The third party function makes some ajax calls, acts on the DOM, i immediately take action.
Is there a neat way of doing this? i hope this is interesting. Thanks.
ps: i though about making params2 global, but i still need an “original” solution 🙂

As for the use of params2, let’s say i want to use different params for every function i want to hook.

examples:

var tmp = foo_1;
foo_1 = function(params1) {
  tmp(params1);
  bar(params2);
}

tmp = foo_2;
foo_2 = function(params1) {
  tmp(params1);
  bar(params3);
}
//etc..

Answer 1

Maybe you should use a simple pubSub system to get notified when foo is called. This will decouple your call of bar from foo.

(function(){
  var footmp = foo;

   foo = function(){
     var result = footmp.apply(this, arguments);
     PubSub.publish('fireBar');
     return result;
  }
})()

PubSub.subscribe( 'fireBar', function(){
 // try to figure out whats params2
 bar(params2)
} );