Variables in JavaScript

Variables are containers for storing data values. They allow you to name and reuse pieces of information in your code.

In modern JavaScript (ES6+), we primarily use let and const. The older var is still supported but has some differences.

Declaring Variables

Use let for variables that can change, and const for values that should not be reassigned.

Reassignment

Variables declared with let can be reassigned. const variables cannot.

var – The Older Way

var is function-scoped and can be hoisted. Prefer let and const in modern code.

Naming Rules

• Names must start with a letter, underscore (_), or dollar sign ($).
• Subsequent characters can include numbers.
• Names are case-sensitive.
• Use camelCase for readability (e.g., myVariableName).

Basic Scope (Block vs Function)

let and const are block-scoped (limited to {} braces). var is function-scoped.

Quick Quiz