Overwrite object method in javascript

Question

I have an object with callback-method which I should extend. The object is elementHandle and method onCheckURLDone(result, data) is called internally somewhere. I need to execute some extended code and call back original function code. I tried something like this:

  var cachedCallback = elementHandle.onCheckURLDone;

  elementHandle.onCheckURLDone = (function(result, data){
    console.log("Some extended code...");

    return function(result, data) {
        return cachedCallback.apply(elementHandle, arguments);
    }
  });

But original code is not called here. What's wrong?

Try removing the return function()... line and the close brace corresponding to it? — Niet the Dark Absol
– Niet the Dark Absol, Commented Feb 20, 2016 at 11:57

madox2 · Accepted Answer · 2016-02-20 12:03:36Z

3

Try this:

var cachedCallback = elementHandle.onCheckURLDone;
elementHandle.onCheckURLDone = function (result, data) {
    console.log('Some extended code...');
    return cachedCallback.apply(elementHandle, arguments);
};

Original callback in your code is called inside returned function. So if you want it to be executed, you have to call it like this:

elementHandle.onCheckURLDone(someResult, someDate)(someResult, someDate);

I suppose it is not what you want.

edited Feb 20, 2016 at 12:03

answered Feb 20, 2016 at 11:58

madox2

52.3k21 gold badges106 silver badges101 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

T.J. Crowder Over a year ago

"try this" answers are not usually useful, there's almost always something useful to say rather than just dumping out code.

Max Frai Over a year ago

It was easy, don't know why I wrote that return wrapper :) Thank you

Collectives™ on Stack Overflow

Overwrite object method in javascript

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related