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JavaScript Case Sensitivity (Live Playground)

JavaScript is a case-sensitive language, which means that variables, function names, and other identifiers must be written with the same capitalization to be recognized as the same. Using different capitalization for the same identifier will cause JavaScript to treat them as separate entities, possibly leading to unexpected behavior in your code.

In this tutorial, we'll explore case sensitivity in JavaScript and learn why consistent naming conventions are essential.

Case Sensitivity in Variables

In JavaScript, variable names with different capitalization are considered different variables. Let's see an example to understand this better:

let myVariable = 10;
let MyVariable = 20;

console.log(myVariable); // Output: 10
console.log(MyVariable); // Output: 20

In the example above, myVariable and MyVariable are treated as separate variables because of their different capitalization. As a result, they can hold different values without any conflict.

Live Playground, Try it Yourself

Case Sensitivity in Functions

Just like variables, function names are also case-sensitive in JavaScript. If you define a function with a certain capitalization and try to call it with a different capitalization, JavaScript will not recognize it, and you will get an error.


function myFunction() {
console.log('Hello, World!');

myFunction(); // Output: Hello, World!
MyFunction(); // ReferenceError: MyFunction is not defined

In the example above, calling myFunction() with the correct capitalization works as expected, but calling MyFunction() with different capitalization results in a ReferenceError, as JavaScript cannot find a function with that name.

Live Playground, Try it Yourself

Importance of Consistent Naming Conventions

To avoid confusion and potential errors caused by case sensitivity, it's crucial to follow consistent naming conventions in your code. One popular convention is camelCase, where the first word of a multi-word identifier is written in lowercase, and the subsequent words have their first letter capitalized.


let firstName = 'John';
let lastName = 'Doe';

function getUserFullName() {
return firstName + ' ' + lastName;

console.log(getUserFullName()); // Output: John Doe

In the example above, we used camelCase for both variable and function names, making the code easier to read and maintain.

Live Playground, Try it Yourself


JavaScript is a case-sensitive language, and identifiers with different capitalizations are treated as separate entities. To avoid confusion and errors, follow a consistent naming convention like camelCase when writing your code. Consistency in capitalization improves code readability and maintainability.