Ways to extend Array object in javascript

arrays, class, extend, javascript

Solution

Method names should be lowercase. Prototype should not be modified in the constructor.

function Array3() { };
Array3.prototype = new Array;
Array3.prototype.add = Array3.prototype.push

in CoffeeScript

class Array3 extends Array
   add: (item)->
     @push(item)

If you don't like that syntax, and you HAVE to extend it from within the constructor, Your only option is:

// define this once somewhere
// you can also change this to accept multiple arguments 
function extend(x, y){
    for(var key in y) {
        if (y.hasOwnProperty(key)) {
            x[key] = y[key];
        }
    }
    return x;
}


function Array3() { 
   extend(this, Array.prototype);
   extend(this, {
      Add: function(item) {
        return this.push(item)
      }

   });
};

You could also do this

ArrayExtenstions = {
   Add: function() {

   }
}
extend(ArrayExtenstions, Array.prototype);



function Array3() { }
Array3.prototype = ArrayExtenstions;

In olden days, 'prototype.js' used to have a Class.create method. You could wrap all this is a method like that

var Array3 = Class.create(Array, {
    construct: function() {

    },    
    Add: function() {

    }
});

For more info on this and how to implement, look in the prototype.js source code

Problem

i try to extend Array object in javascript with some user friendly methods like Array.Add() instead Array.push() etc... i implement 3 ways to do this. unfortunetly the 3rd way is not working and i want to ask why? and how to do it work. ``` //------------- 1st way Array.prototype.Add=function(element){ this.push(element); }; var list1 = new Array(); list1.Add("Hello world"); alert(list1[0]); //------------- 2nd way function Array2 () { //some other properties and methods }; Array2.prototype = new Array; Array2.prototype.Add = function(element){ this.push(element); }; var list2 = new Array2; list2.Add(123); alert(list2[0]); //------------- 3rd way function Array3 () { this.prototype = new Array; this.Add = function(element){ this.push(element); }; }; var list3 = new Array3; list3.Add(456); //push is not a function alert(list3[0]); // undefined ``` in 3rd way i want to extend the Array object internally Array3 class. How to do this so not to get "push is not a function" and "undefined"? Here i add a 4th way. ``` //------------- 4th way function Array4 () { //some other properties and methods this.Add = function(element){ this.push(element); }; }; Array4.prototype = new Array(); var list4 = new Array4(); list4.Add(789); alert(list4[0]); ``` Here again i have to use prototype. I hoped to avoid to use extra lines outside class constructor as Array4.prototype. I wanted to have a compact defined class with all pieces in one place. But i think i cant do it otherwise.

Original source