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JavaScript - Static Methods

What are Static Methods?

A static method in JavaScript is defined using the static keyword followed by the method name. You can execute the static method by taking the class name as a reference rather than an instance of the class.

The main benefit of the static method is that it can be used to create a utility function that doesn't require the instance of the class for the execution. For example, a Math object contains various static methods, which we can invoke through Math class directly.

Also, you can use static methods to add all related methods under a single namespace. Furthermore, static methods give better performance than the regular class methods due to memory optimization.

In the following syntax, we define a static method called getSize() in the class called Table −

class Table {
	static getSize() { // Static method
		return "10 x 10";
	}
}
Table.getSize(); // Static method invocation

In the above syntax, getSize() is a static method. We used the class name to execute the getSize() method.

Examples

Let's understand the JavaScript static methods with the help of some examples of difference use-cases −

Example: Static Method

In the example below, printSize() is a static method, and getSize() is a regular method in the table class. You can see that printSize() method is invoked using the table class name, and getSize() method is executed using the class instance.

So, the class can contain static and non-static both methods.

<html>
<body>
	<p id = "demo"> </p>
	<script>
		const output = document.getElementById("demo");

		class Table {
			static printSize() {
				return "The size of the table is: 20 x 20 <br>";
			}

			getColor() {
				return "Black";
			}
		}

		output.innerHTML = Table.printSize(); // Static method execution
		const tableObj = new Table();
		output.innerHTML += "The color of the table is: " + tableObj.getColor();
	</script>
</body>
</html>

Output

The size of the table is: 20 x 20
The color of the table is: Black

The single class can also contain multiple static methods.

Example: Multiple Static Methods

In the below code, the table class contains the printSize() and getSize() static methods. Both methods are executed by taking the class name as a reference.

<html>
<body>
	<p id = "output"> </p>
	<script>
		class Table {
			static printSize() {
				return "The size of the table is 20 x 20 <br>";
			}

			static getColor() {
				return "The color of the table is Pink";
			}
		}

		document.getElementById("output").innerHTML = 
		Table.printSize() + "br" +
		Table.getColor();
	</script>
</body>
</html>

Output

The size of the table is 20 x 20
brThe color of the table is Pink

A single class can contain multiple static methods with the same name. When you execute the static method with the same name, it executes the last method.

Example: Static Methods with the Same Name

In the example below, the table class contains the duplicate printSize() method. In the output, you can observe that the code executes the second printSize() method.

<html>
<body>
	<p id = "output"> </p>
	<script>
		class Table {
			static printSize() {
				return"The size of the table is: 20 x 20 <br>";
			}

			static printSize() {
				return "The size of the table is: 30 x 30 <br>";
			}
		}
		document.getElementById("output").innerHTML = Table.printSize(); // Static method execution
	</script>
</body>
</html>

Output

The size of the table is: 30 x 30

You can also execute the static method of the class in the constructor. You can use this keyword followed by the constructor keyword followed by the static method name to execute the static method in the constructor.

Example: Static Method Execution in the Constructor

In the example below, the Num class contains the getSqrt() static method. We have executed the getSqrt() method in the constructor.

Whenever you create a new object of the Num class, it will store the square root of the number in the 'sqrt' property of the class.

<html>
<body>
	<p id = "output">The square root of the 10 is: </p>
	<script>
		class Num {
			constructor(a) {
				// Static method execution
				this.sqrt = this.constructor.getSqrt(a);
			}

			static getSqrt(a) {
				return a * a;
			}
		}
		const num1 = new Num(10);
		document.getElementById("output").innerHTML += num1.sqrt;
	</script>
</body>
</html>

Output

The square root of the 10 is: 100

You can also execute the static method in the non-static method. You need to use the class name as a reference to execute the static method in the non-static method.

Example: Static Method Execution in Non-Static Method

In the example below, getSqrt() is a static method, and printSqrt() is a regular class method. In the printSqrt() method, we execute the getSqrt() method.

We used the instance of the Num class to execute the printSqrt() method.

<html>
<body>
	<p id = "demo"> </p>
	<script>
		const output = document.getElementById("demo");
		class Num {
			static getSqr(a) {
				return a * a;
			}

			printSqr(a) {
				output.innerHTML += "The square of " + a + " is: " + Num.getSqr(a) + "<br>";
			}
		}
		const num1 = new Num();
		num1.printSqr(6);
	</script>
</body>
</html>

Output

The square of 6 is: 36
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