JavaScript Statement & Expression

JavaScript Identifiers

JavaScript identifiers are names used to identify variables, functions, objects, classes, and other items in code.

Example

javascript

let userName = "Amit";

Here, userName is an identifier.

What are Identifiers?

An identifier is simply a name given to something in JavaScript.

You use identifiers to name:

Item	Example
Variable	`let age = 25;`
Function	`function showMessage() {}`
Object	`let student = {};`
Class	`class User {}`

Example

javascript

let courseName = "JavaScript";

function showCourse() {
  console.log(courseName);
}

In this example, courseName and showCourse are identifiers.

Rules for JavaScript Identifiers

JavaScript identifiers must follow some rules.

Rule	Valid Example	Invalid Example
Can contain letters	`name`
Can contain digits, but not at the beginning	`name1`	`1name`
Can contain underscore `_`	`user_name`
Can contain dollar sign `$`	`$price`
Cannot contain spaces	`userName`	`user name`
Cannot be a JavaScript keyword	`userAge`	`let`
Are case-sensitive	`name`, `Name`

Valid Identifier Examples

These are valid JavaScript identifiers:

Example

javascript

let name = "Amit";
let userName = "Rahul";
let user_age = 25;
let $price = 500;
let totalAmount1 = 1000;

All these names follow JavaScript identifier rules.

Invalid Identifier Examples

These are invalid JavaScript identifiers:

Example

javascript

let 1name = "Amit";
let user name = "Rahul";
let user-name = "Amit";
let let = "JavaScript";

These are invalid because:

Identifier	Problem
`1name`	Starts with a number
`user name`	Contains a space
`user-name`	Hyphen is not allowed
`let`	JavaScript keyword

Identifiers are Case-Sensitive

JavaScript identifiers are case-sensitive.

This means name, Name, and NAME are different identifiers.

Example

javascript

let name = "Amit";
let Name = "Rahul";
let NAME = "Suman";

JavaScript treats all three as different variables.

Good Identifier Names

A good identifier should clearly describe what it stores or does.

Good examples:

Example

javascript

let studentName = "Amit";
let totalPrice = 1500;
let isLoggedIn = true;

function calculateTotal() {
  // code here
}

These names are easy to understand.

Poor Identifier Names

Avoid unclear names when writing beginner-friendly or real project code.

Example:

Example

javascript

let x = "Amit";
let y = 1500;
let z = true;

These names work, but they do not clearly explain what the values mean.

A better version:

Example

javascript

let studentName = "Amit";
let totalPrice = 1500;
let isLoggedIn = true;

camelCase Naming

In JavaScript, camelCase is commonly used for variable and function names.

In camelCase, the first word starts with a lowercase letter, and each next word starts with an uppercase letter.

Example

javascript

let firstName = "Amit";
let totalPrice = 500;
let userEmailAddress = "amit@example.com";

function showUserName() {
  console.log(firstName);
}

camelCase makes names readable and clean.

Identifiers with Functions

Function names are also identifiers.

Example

javascript

function showMessage() {
  console.log("Hello JavaScript");
}

Here, showMessage is an identifier.

Function names should describe the action they perform.

Good examples:

Example

javascript

function calculateTotal() {}
function showAlert() {}
function validateForm() {}
function getUserName() {}

Identifiers with Objects

Object property names can also be identifiers.

Example

javascript

let student = {
  name: "Amit",
  age: 20,
  course: "JavaScript"
};

Here, student, name, age, and course are identifiers.

You can access object values like this:

Example

javascript

console.log(student.name);
console.log(student.course);

Complete Example

html

<!DOCTYPE html>
<html>
<head>
  <title>JavaScript Identifiers</title>
</head>
<body>

  <h1>JavaScript Identifiers</h1>

  <p id="result"></p>

  <script>
    let studentName = "Amit";
    let courseName = "JavaScript";
    let courseFee = 999;

    function showDetails() {
      document.getElementById("result").innerHTML =
        studentName + " is learning " + courseName +
        ". Course fee is " + courseFee + ".";
    }

    showDetails();
  </script>

</body>
</html>

Try It Yourself

Run the above example in the Try It Editor.

Try changing the identifier names such as studentName, courseName, and showDetails.

Make sure the new names follow JavaScript identifier rules.

Important Points

Identifiers are names used for variables, functions, objects, classes, and more.
Identifiers can contain letters, digits, underscore, and dollar sign.
Identifiers cannot start with a number.
Identifiers cannot contain spaces.
Identifiers cannot be JavaScript keywords.
JavaScript identifiers are case-sensitive.
camelCase is commonly used for variable and function names in JavaScript.

Conclusion

JavaScript identifiers are names used to identify different parts of a program.

Good identifiers make code easier to read and understand.

When writing JavaScript, always use meaningful names that follow identifier rules and clearly describe the purpose of the variable, function, or object.

PreviousJavaScript Keywords NextJavaScript Case Sensitivity