JavaScript Keywords and Identifiers
In this tutorial, you will learn about JavaScript keywords and identifiers with the help of examples.
JavaScript Keywords
Keywords are reserved words that are part of the syntax in the programming language. For example,
const a = 'hello';
Here, const is a keyword that denotes that a is a constant.
Keywords cannot be used to name identifiers.
Here is the list of keywords available in JavaScript.
await |
break |
case |
catch |
class |
const |
continue |
debugger |
default |
delete |
do |
else |
enum |
export |
extends |
false |
finally |
for |
function |
if |
implements |
import |
in |
instanceof |
interface |
let |
new |
null |
package |
private |
protected |
public |
return |
super |
switch |
static |
this |
throw |
try |
true |
typeof |
var |
void |
while |
with |
yield |
JavaScript Identifiers
An identifier is a name that is given to entities like variables, functions, class, etc.
Rules for Naming JavaScript Identifiers
The rules for writing identifiers are:
- Identifier names must start with either a letter, an underscore
_, or the dollar sign$.For example,//valid const a = 'hello'; const _a = 'hello'; const $a = 'hello'; - Identifier names cannot start with numbers. For example,
//invalid const 1a = 'hello'; // this gives an error - JavaScript is case-sensitive. So y and Y are different identifiers. For example,
const y = "hi"; const Y = 5; console.log(y); // hi console.log(Y); // 5 - Keywords cannot be used as identifier names. For example,
//invalid const new = 5; // Error! new is a keyword.
Note: Though you can name identifiers in any way you want, it's a good practice to give a descriptive identifier name.
If you are using an identifier for a variable to store the number of students, it is better to use students or numberOfStudents rather than x or n.
