---
title: Object ECMAScript 5
description: "ECMAScript 5 added a lot of new Object Methods to JavaScript. ### ES5 New Object Methods `// Adding or changing an object property Object.defineProperty(object, property, descriptor) // Adding or changing many object properties Object.defineProperties(object, descriptors) // Accessing Properties Object.getOwnPropertyDescriptor(object, property)…"
url: "https://apprentice.mn/docs/object-ecmascript-5/"
updated: "2021-05-18"
category: Javascript
---

# Object ECMAScript 5

ECMAScript 5 added a lot of new Object Methods to JavaScript.

### ES5 New Object Methods

      `// Adding or changing an object property
Object.defineProperty(object, property, descriptor)

// Adding or changing many object properties
Object.defineProperties(object, descriptors)

// Accessing Properties
Object.getOwnPropertyDescriptor(object, property)

// Returns all properties as an array
Object.getOwnPropertyNames(object)

// Returns enumerable properties as an array
Object.keys(object)

// Accessing the prototype
Object.getPrototypeOf(object)

// Prevents adding properties to an object
Object.preventExtensions(object)
// Returns true if properties can be added to an object
Object.isExtensible(object)

// Prevents changes of object properties (not values)
Object.seal(object)
// Returns true if object is sealed
Object.isSealed(object)

// Prevents any changes to an object
Object.freeze(object)
// Returns true if object is frozen
Object.isFrozen(object)`

## Changing a Property Value

### Syntax

      `Object.defineProperty(object, property, {value : value})`

This example changes a property value:

### Example

      `var person = {
  firstName: "John",
  lastName : "Doe",
  language : "EN"
};

// Change a property
Object.defineProperty(person, "language", {value : "NO"});`

## Changing Meta Data

ES5 allows the following property meta data to be changed:

       `writable : true      // Property value can be changed
enumerable : true    // Property can be enumerated
configurable : true  // Property can be reconfigured

writable : false     // Property value can not be changed
enumerable : false   // Property can be not enumerated
configurable : false // Property can be not reconfigured`

ES5 allows getters and setters to be changed:

     `// Defining a getter
get: function() { return language }
// Defining a setter
set: function(value) { language = value }`

This example makes language read-only:

       `Object.defineProperty(person, "language", {writable:false});`

This example makes language not enumerable:

       `Object.defineProperty(person, "language", {enumerable:false});`

## Listing All Properties

This example list all properties of an object:

### Example

      `var person = {
  firstName: "John",
  lastName : "Doe",
  language : "EN"
};

Object.defineProperty(person, "language", {enumerable:false});
Object.getOwnPropertyNames(person);  // Returns an array of properties`

## Listing Enumerable Properties

This example list only the enumerable properties of an object:

### Example

      `var person = {
  firstName: "John",
  lastName : "Doe",
  language : "EN"
};

Object.defineProperty(person, "language", {enumerable:false});
Object.keys(person);  // Returns an array of enumerable properties`

## Adding a Property

This example adds a new property to an object:

### Example

      `// Create an object:
var person = {
  firstName: "John",
  lastName : "Doe",
  language : "EN"
};

// Add a property
Object.defineProperty(person, "year", {value:"2008"});`

## Adding Getters and Setters

The `Object.defineProperty()` method can also be used to add Getters and Setters:

### Example

      `//Create an object
var person = {firstName:"John", lastName:"Doe"};

// Define a getter
Object.defineProperty(person, "fullName", {
  get : function () {return this.firstName + " " + this.lastName;}
});`

## A Counter Example

### Example

      `// Define object
var obj = {counter:0};

// Define setters
Object.defineProperty(obj, "reset", {
  get : function () {this.counter = 0;}
});
Object.defineProperty(obj, "increment", {
  get : function () {this.counter++;}
});
Object.defineProperty(obj, "decrement", {
  get : function () {this.counter--;}
});
Object.defineProperty(obj, "add", {
  set : function (value) {this.counter += value;}
});
Object.defineProperty(obj, "subtract", {
  set : function (i) {this.counter -= i;}
});

// Play with the counter:
obj.reset;
obj.add = 5;
obj.subtract = 1;
obj.increment;
obj.decrement;`        [https://www.addtoany.com/add_to/facebook?linkurl=https%3A%2F%2Fapprentice.mn%2Fdocs%2Fobject-ecmascript-5%2F&linkname=Object%20ECMAScript%205](https://www.addtoany.com/add_to/facebook?linkurl=https%3A%2F%2Fapprentice.mn%2Fdocs%2Fobject-ecmascript-5%2F&linkname=Object%20ECMAScript%205)[https://www.addtoany.com/add_to/mastodon?linkurl=https%3A%2F%2Fapprentice.mn%2Fdocs%2Fobject-ecmascript-5%2F&linkname=Object%20ECMAScript%205](https://www.addtoany.com/add_to/mastodon?linkurl=https%3A%2F%2Fapprentice.mn%2Fdocs%2Fobject-ecmascript-5%2F&linkname=Object%20ECMAScript%205)[https://www.addtoany.com/add_to/email?linkurl=https%3A%2F%2Fapprentice.mn%2Fdocs%2Fobject-ecmascript-5%2F&linkname=Object%20ECMAScript%205](https://www.addtoany.com/add_to/email?linkurl=https%3A%2F%2Fapprentice.mn%2Fdocs%2Fobject-ecmascript-5%2F&linkname=Object%20ECMAScript%205)[https://www.addtoany.com/share](https://www.addtoany.com/share)