JavaScript var Keyword

The var keyword in JavaScript is used to declare variables. Before ES6 introduced let and const, var was the only way to declare variables. Although still valid, it's now considered outdated due to its function scope and hoisting behavior, which can lead to bugs.

Syntax

Example: Using var

Key Features of var

1. Function Scope

Variables declared with var are limited to the function, not the block.

⚠️ var is not block-scoped — which may lead to unexpected results.

2. Hoisting

var declarations are hoisted to the top of their function or global scope.

Is interpreted as:

Only the declaration is hoisted, not the assignment.

3. Can Be Redeclared and Reassigned

You can freely redeclare and reassign variables declared with var in the same scope.

When to Use var

• In legacy JavaScript codebases
• When function-scoping is explicitly needed
• ❌ Avoid in modern development; prefer let or const

Key Takeaways

• var is function-scoped, not block-scoped
• var is hoisted, which can cause confusion if misused
• It allows re-declaration and reassignment in the same scope
• Not recommended in modern JavaScript—use let and const instead
• Still important to understand for debugging or maintaining older code