THE WORLD'S LARGEST WEB DEVELOPER SITE
×

JS Tutorial

JS HOME JS Introduction JS Where To JS Output JS Statements JS Syntax JS Comments JS Variables JS Operators JS Arithmetic JS Assignment JS Data Types JS Functions JS Objects JS Events JS Strings JS String Methods JS Numbers JS Number Methods JS Arrays JS Array Methods JS Array Sort JS Array Iteration JS Dates JS Date Formats JS Date Get Methods JS Date Set Methods JS Math JS Random JS Booleans JS Comparisons JS Conditions JS Switch JS Loop For JS Loop While JS Break JS Type Conversion JS Bitwise JS RegExp JS Errors JS Scope JS Hoisting JS Strict Mode JS this Keyword JS Let JS Const JS Debugging JS Style Guide JS Best Practices JS Mistakes JS Performance JS Reserved Words JS Versions JS Version ES5 JS Version ES6 JS JSON

JS Forms

JS Forms Forms API

JS Objects

Object Definitions Object Properties Object Methods Object Accessors Object Constructors Object Prototypes Object ECMAScript 5

JS Functions

Function Definitions Function Parameters Function Invocation Function Call Function Apply Function Closures

JS HTML DOM

DOM Intro DOM Methods DOM Document DOM Elements DOM HTML DOM CSS DOM Animations DOM Events DOM Event Listener DOM Navigation DOM Nodes DOM Collections DOM Node Lists

JS Browser BOM

JS Window JS Screen JS Location JS History JS Navigator JS Popup Alert JS Timing JS Cookies

JS AJAX

AJAX Intro AJAX XMLHttp AJAX Request AJAX Response AJAX XML File AJAX PHP AJAX ASP AJAX Database AJAX Applications AJAX Examples

JS JSON

JSON Intro JSON Syntax JSON vs XML JSON Data Types JSON Parse JSON Stringify JSON Objects JSON Arrays JSON PHP JSON HTML JSON JSONP

JS Examples

JS Examples JS HTML DOM JS HTML Input JS HTML Objects JS HTML Events JS Browser JS Quiz JS Certificate

JS References

JavaScript Objects HTML DOM Objects


JavaScript Object Accessors


JavaScript Accessors (Getters and Setters)

ECMAScript 5 (2009) introduced Getter and Setters.

Getters and setters allow you to define Object Accessors (Computed Properties).


JavaScript Getter (The get Keyword)

This example uses a lang property to get the value of the language property.

Example

// Create an object:
var person = {
    firstName: "John",
    lastName : "Doe",
    language : "en",
    get lang() {
        return this.language;
    }
};
// Display data from the object using a getter:
document.getElementById("demo").innerHTML = person.lang;
Try it Yourself »

JavaScript Setter (The set Keyword)

This example uses a lang property to set the value of the language property.

Example

var person = {
    firstName: "John",
    lastName : "Doe",
    language : "",
    set lang(lang) {
        this.language = lang;
    }
};
// Set an object property using a setter:
person.lang = "en";
// Display data from the object:
document.getElementById("demo").innerHTML = person.language;
Try it Yourself »


JavaScript Function or Getter?

What is the differences between these two examples?

Example 1

var person = {
    firstName: "John",
    lastName : "Doe",
    fullName : function() {
        return this.firstName + " " + this.lastName;
    }
};
// Display data from the object using a method:
document.getElementById("demo").innerHTML = person.fullName();
Try it Yourself »

Example 2

var person = {
    firstName: "John",
    lastName : "Doe",
    get fullName() {
        return this.firstName + " " + this.lastName;
    }
};
// Display data from the object using a getter:
document.getElementById("demo").innerHTML = person.fullName;
Try it Yourself »

Example 1 access fullName as a function: person.fullName().

Example 2 access fullName as a property: person.fullName.

The second example provides simpler syntax.


Data Quality

JavaScript can secure better data quality when using getters and setters.

Using the lang property, in this example, returns the value of the language property in upper case:

Example

// Create an object:
var person = {
    firstName: "John",
    lastName : "Doe",
    language : "en",
    get lang() {
        return this.language.toUpperCase();
    }
};
// Display data from the object using a getter:
document.getElementById("demo").innerHTML = person.lang;
Try it Yourself »

Using the lang property, in this example, stores an upper case value in the language property:

Example

var person = {
    firstName: "John",
    lastName : "Doe",
    language : "",
    set lang(lang) {
        this.language = lang.toUpperCase();
    }
};
// Set an object property using a setter:
person.lang = "en";
// Display data from the object:
document.getElementById("demo").innerHTML = person.language;
Try it Yourself »

Why Using Getters and Setters?

  • It gives simpler syntax
  • It allows equal syntax for properties and methods
  • It can secure better data quality
  • It is useful for doing things behind-the-scenes

A Counter Example

Example

var obj = {
    counter : 0,
    get reset() {
      this.counter = 0;
    },
    get increment() {
      this.counter++;
    },
    get decrement() {
      this.counter--;
    },
    set add(value) {
      this.counter += value;
    },
    set subtract(value) {
      this.counter -= value;
    }
};
// Play with the counter:
obj.reset;
obj.add = 5;
obj.subtract = 1;
obj.increment;
obj.decrement;
Try it Yourself »

Object.defineProperty()

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

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;
Try it Yourself »

Browser Support

Getters and Setters are not supported in Internet Explorer 8 or earlier:

Yes 9.0 Yes Yes Yes