JavaScript Inheritance [closed]

Question

I am trying to implement inheritance in javascript. I came up with following minimal code to support it.

function Base(){     this.call = function(handler, args){       handler.call(this, args);     } }  Base.extend = function(child, parent){     parent.apply(child);     child.base = new parent;     child.base.child = child; } 

Experts, please let me know if this will be sufficient or any other important issue I may have missed. Based on similar issues faced please suggest other changes.

Here is complete test script:

function Base(){     this.call = function(handler, args){       handler.call(this, args);     }     this.superalert = function(){         alert('tst');     } }  Base.extend = function(child, parent){     parent.apply(child);     child.base = new parent;     child.base.child = child; }  function Child(){     Base.extend(this, Base);     this.width = 20;     this.height = 15;     this.a = ['s',''];     this.alert = function(){         alert(this.a.length);         alert(this.height);     } }  function Child1(){     Base.extend(this, Child);     this.depth = 'depth';     this.height = 'h';     this.alert = function(){         alert(this.height); // display current object height         alert(this.a.length); // display parents array length         this.call(this.base.alert);            // explicit call to parent alert with current objects value         this.call(this.base.superalert);            // explicit call to grandparent, parent does not have method          this.base.alert(); // call parent without overriding values     } }  var v = new Child1(); v.alert(); alert(v.height); alert(v.depth); 

Answer 1

To implement javascript inheritance in ECMAScript 5 you can define the prototype of an object and use Object.create to inherit. You can also add/override properties as much as you want.

Example:

/**  * Transform base class  */ function Transform() {     this.type = "2d"; }  Transform.prototype.toString = function() {     return "Transform"; }  /**  * Translation class.  */ function Translation(x, y) {     // Parent constructor     Transform.call(this);      // Public properties     this.x = x;     this.y = y; }  // Inheritance Translation.prototype = Object.create(Transform.prototype);  // Override Translation.prototype.toString = function() {     return Transform.prototype.toString() + this.type + " Translation " + this.x + ":" + this.y; }  /**  * Rotation class.  */ function Rotation(angle) {     // Parent constructor     Transform.call(this);      // Public properties     this.angle = angle; }  // Inheritance Rotation.prototype = Object.create(Transform.prototype);  // Override Rotation.prototype.toString = function() {     return Transform.prototype.toString() + this.type + " Rotation " + this.angle; }  // Tests translation = new Translation(10, 15);  console.log(translation instanceof Transform); // true console.log(translation instanceof Translation); // true console.log(translation instanceof Rotation); // false  console.log(translation.toString()) // Transform2d Translation 10:15