[Javascript] Callback function

Callback在寫oop的javascript中非常好用， 找到了一篇非常容易理解的好文章。
Callback Functions in JavaScript

function mySandwich(param1, param2, callback) {
    alert('Started eating my sandwich.\n\nIt has: ' + param1 + ', ' + param2);
    if (callback && typeof(callback) === "function") {
        callback();
    }
}

mySandwich('ham', 'cheese', 'vegetables');