JavaScript Reserved Words

JavaScript has a set of reserved words that have specific meanings within the language and cannot be used as identifiers for variables, functions, or other elements. Understanding these reserved words is crucial for avoiding errors and ensuring that your code runs smoothly. This article outlines the reserved words in JavaScript and explains their significance.

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What Are Reserved Words?

Reserved words in JavaScript are keywords that are used by the language itself to perform specific operations or define functionality. These words are predefined and have special meanings, so they cannot be used as variable names, function names, or identifiers.

For example, using a reserved word like class as a variable name will result in a syntax error because class is a keyword used for defining classes in JavaScript.

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List of JavaScript Reserved Words

Here is a list of reserved words that you should avoid using as identifiers in your JavaScript code:

Keywords:

Keywords
break	case	catch	class	const	continue
debugger	default	delete	do	else	export
extends	finally	for	function	if	import
in	instanceof	new	return	super	switch
throw	try	typeof	var	void	while
with	yield

Future Reserved Words:

Future Reserved Words
enum	implements	interface	let
package	private	protected	public
static

Literal Values:

Literal Values
null	true	false

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Examples of Reserved Words in Use

Let’s take a look at a few examples of how reserved words are used and what happens if you try to use them as identifiers.

Valid Usage of Reserved Words

class Person {
  constructor(name) {
    this.name = name;
  }
}

const person = new Person('John');
console.log(person.name); // John

In this example, class and const are used as JavaScript keywords to define a class and a constant variable, respectively.

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Invalid Usage of Reserved Words

const class = 'Math'; // SyntaxError: Unexpected token 'class'

Here, class is incorrectly used as a variable name, which will throw a syntax error because class is a reserved word in JavaScript.

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Conclusion

JavaScript reserved words are essential to the language and are reserved for specific functionalities. It’s important to avoid using these words as variable names, function names, or identifiers in your code. Familiarizing yourself with this list of reserved words will help you write error-free and well-structured JavaScript code.