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const in JavaScript

JavaScript const: Here, we are going to learn about the const in JavaScript, how to create a constant in JavaScript?
Submitted by IncludeHelp, on February 01, 2019

JavaScript - const

Like other programming languages, JavaScript also provide the feature to create constants, we can make any identifier as constant by using the "const".

Declare constant

"const" is a keyword in JavaScript and it makes an identifier constant.

Syntax

const identifier_name = value;

Points to remember

While creating a constant, a value should be assigned.
A constant's value cannot be changed.

Error

If we try to change the value of a constant following type error throws:

TypeError: Assignment to constant variable.

Example of const in JavaScript

<html>
<head>
<title>JavaScipt Example</title>
</head>

<body>
	<script>		
		const url = "www.example.com";
		const port_no = 25;
		
		//printing...
		document.write("url: " + url + "<br>");
		document.write("port_no: " + port_no + "<br>");
		
		//if you will try to change the value
		//it will not be changed
		try{
		port_no = 21;		
		}
		catch(err){
			document.write(err + "<br>");
		}
	</script>
</body>
</html>

Output

url: www.example.com
port_no: 25
TypeError: Assignment to constant variable.