Getting a better understanding of callback functions in JavaScript

javascript function callback
user4903 picture user4903 · Jan 27, 2009 · Viewed 207.4k times · Source

I understand passing in a function to another function as a callback and having it execute, but I'm not understanding the best implementation to do that. I'm looking for a very basic example, like this:

var myCallBackExample = {
    myFirstFunction : function( param1, param2, callback ) {
        // Do something with param1 and param2.
        if ( arguments.length == 3 ) {
            // Execute callback function.
            // What is the "best" way to do this?
        }
    },
    mySecondFunction : function() {
        myFirstFunction( false, true, function() {
            // When this anonymous function is called, execute it.
        });
    }
};

In myFirstFunction, if I do return new callback(), then it works and executes the anonymous function, but that doesn't seem like the correct approach to me.

Answer

krosenvold picture krosenvold · Jan 27, 2009

You can just say

callback();

Alternately you can use the call method if you want to adjust the value of this within the callback.

callback.call( newValueForThis);

Inside the function this would be whatever newValueForThis is.

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