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JavaScript - Object Methods

JavaScript Object Methods

JavaScript object methods are object properties that contains function definitions. An object is a collection of properties, and a property is an association between a name (or key) and a value. A property's value can be a function; in that case the property is known as a method.

You can either directly add a method to the object or add it as a property value. The method can also take the parameters and return the value. Object methods are a powerful way to add functionality to objects. They allow you to encapsulate code and make it reusable.

Syntax

Follow the syntax below to add a method to the object.

const obj = {
	sum: function () {
		// Method body
	}
}
obj.sum();

In the above syntax, 'sum' is a method defined inside the 'obj' object. You can access the method as you access the object property and add the pair of parenthesis to invoke the method.

Example

We added the getInfo() method in the 'company' object in the example below. The getInfo() method returns the string containing the object properties.

Here, we used the 'this' keyword to access the object properties inside the object. The 'this' keyword represents the object itself.

After that, we used the object as a reference to invoke the method.

<html>
<body>
	<p>Company Information</p>
	<p id = "output"> </p>
	<script>
		const company = {
		   companyName: "Tutorials Point",
			companyWebsite: "www.tutorialspoint.com",

			getInfo: function () {
				return "Comapny Name: " + this.companyName +"<br>Website: " + this.companyWebsite;
			},
		}
		document.getElementById("output").innerHTML = company.getInfo();
	</script>
</body>
</html>

Output

Company Information

Comapny Name: Tutorials Point
Website: www.tutorialspoint.com

Object Method Shorthand

The ES6 provides the shortest way to define a method into the object.

Syntax

Follow the syntax below to add a method to the object.

const Obj = {
   sum() {
   // Method body
   }
}
Obj.sum();

Like the previous one, you can access and invoke the method in the above syntax.

Example

In the example below, we defined the getInfo() method as the previous example.

<html>
<body>
	<p id = "output"> </p>
	<script>
		const employee = {
			name: "John Doe",
			age: 32,
			getInfo() {
				return "The employee name is " + this.name + " and his age is " + this.age + " Years.";
			},
		}
    
		document.getElementById("output").innerHTML = employee.getInfo();
    
	</script>
</body>
</html>

Output

The employee name is John Doe and his age is 32 Years.

Example

The example below defines the getSum() method inside the 'nums' object. The getSum() method takes the two parameters and returns their sum.

We passed the number arguments to the method while invoking it.

<html>
<body>
	<p id = "output">The sum of 2 and 3 is  </p>
	<script>
		const nums = {
			getSum(a, b) {
				return a + b;
			}
		}
		document.getElementById("output").innerHTML += nums.getSum(2, 3);
	</script>
</body>
</html>

Output

The sum of 2 and 3 is 5

Updating or Adding a Method to the Object

In JavaScript, updating or adding a new method to the object is same as updating or adding new proeprties to the object. You can either use the dot or square bracket notation to update or add method to the object.

Example

The example below defines the getSum() method inside the 'nums' object.

After that, we add the getMul() method inside the nums object. We invoke the getMul() method by passing two arguments to get the multiplication of them.

<html>
<body>
	<p id = "output">The multiplication of 2 and 3 is </p>
	<script>
		const nums = {
			getSum(a, b) {
			return a + b;
			}
		}
		nums.getMul = function (a, b) {
			return a * b;
		}
    
		document.getElementById("output").innerHTML += nums.getMul(2, 3);
	</script>
</body>
</html>

Output

The multiplication of 2 and 3 is 6

Using Built-in Methods

JavaScript objects like string, number, boolean, etc., also contain built-in methods. You can execute them by taking the object as a reference.

Example

In the example below, we have defined the 'num' variable containing the numeric value. After that, we used the toString() method to convert the number to a string.

<html>
<body>
	<p id = "demo"> </p>
	<script>
		const output = document.getElementById("demo");
		const num = new Number(20);
		let str = num.toString();
		output.innerHTML += "After converting the number to string: " + str + "<br>";
		output.innerHTML += "Data type of after conversion: " + typeof str;
	</script>
</body>
</html>

Output

After converting the number to string: 20
Data type of after conversion: string
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