Creating Variables with var

We've been using let and const to create variables, but there's a third option var that also allows you to create variables.

What is var?

The var keyword works similarly to let for basic variable creation:

Copyvar a = 1
console.log(a) // 1
a = 2
console.log(a) // 2

This looks identical to using let, but var behaves very differently under the hood.

Why var Exists

Originally, when JavaScript was first created, var was the only way to create variables. Later, let and const were added to fix the strange and confusing behavior of var.

Problems With var

While var can be used to create variables, it has several issues that make it problematic:

var Uses Function Scope

The biggest issue with var is that it completely ignores block scope and uses function scope instead:

Copyfunction func() {
  {
    var a = 1 // Function scope
  }
  console.log(a) // Prints 1
}

func()

Copyfunction func() {
  {
    let a = 1 // Block scope
  }
  console.log(a) // ❌ ReferenceError: a is not defined
}

func()

var Gets Hoisted Strangely

Variables declared with var get hoisted to the top of their scope, but only the declaration (not the value):

Copyconsole.log(a) // Prints undefined
var a = 1
console.log(a) // 1

JavaScript treats this as if you wrote:

Copyvar a
console.log(a) // Prints undefined
a = 1 // Assignment happens here
console.log(a) // 1

Here is how it behaves with let:

Copyconsole.log(a) // ❌ ReferenceError: Cannot access 'a' before initialization
let a = 1

var Allows Redeclaration

You can declare the same var variable multiple times, which can lead to confusion:

Copyvar a = 1
var a = 2 // No error - just overwrites the first one
console.log(a) // 2

With let, you get a helpful error:

Copylet b = 1
let b = 2 // ❌ SyntaxError: Identifier 'b' has already been declared

When You Might See var

1. Older codebases - Code written before let and const existed
2. Legacy tutorials - Outdated learning materials
3. Interview questions - Testing your understanding of JavaScript quirks

Best Practice

• Never use var in modern JavaScript

The only reason to know about var is to understand legacy code and avoid its pitfalls when you encounter it.