Attach event listener to Array push method call

attach-listener-to-push-method.js

var eventify = function(arr, callback) {
    arr.push = function(e) {
        Array.prototype.push.call(arr, e);
        callback(arr);
    };
};

var array = [1,2,3];

eventify(array, function(newArray) {
  alert("new array length is:" + newArray.length);
});

array.push(4); // alerts new array length is: 4
array.push(5); // alerts new array length is: 5