Questions tagged [callback]

In computer programming, a callback is a piece of executable code that is passed as an argument to other code, which is expected to call back (execute) the argument at some convenient time. The invocation may be immediate as in a synchronous callback or it might happen at later time, as in an asynchronous callback.

Wikipedia article: http://en.wikipedia.org/wiki/Callback_(computer_programming)

function outer(argumentOne, fn){
    console.log("what was argumentOne? ", argumentOne);
    return fn();
}

function someCallback() {
    console.log("callback triggered!");
}

outer("brown", someCallback);

An example of async process callback in javascript:

function mySandwich(param1, param2, callback) {
        console.log('Started eating my sandwich.\n\n It has: ' + param1 + ', ' + param2);
    setTimeout(function(){
        callback(null,param1*param2);},2000);
    }

    mySandwich(1, 2, function(err,result) {
        console.log('Finished eating my sandwich.' + result);
    });

Output:

Started eating my sandwich.

It has: 1, 2
Finished eating my sandwich.2