🔄 Type Casting (Type Conversion)

Last Updated: 08 Oct 2025

Type Casting or Type Conversion means changing data from one type to another.

In JavaScript, this can happen automatically (implicit) or manually (explicit).

Hinglish Tip 🗣: Jaise ek glass me paani ya juice daal kar uska type badal jaata hai, waise hi variable ke data ka type badalne ko type casting kehte hain.

Type of Type Casting

There are two types of type casting:

  • Implicit Conversion (Type Coercion) → Done automatically by JavaScript.
  • Explicit Conversion (Manual Casting) → Done by developer using functions like Number(), String(), etc.

Implicit Conversion

// Number+String = String
let result = 10 + "5";
console.log(result); // "105"
console.log(typeof result); // "string"

// String*Number = Number
let result = "10" * 5;
console.log(result); // 50
console.log(typeof result); // "number"

// Boolean+Number = Number
let result = true + 5;
console.log(result); // 6
console.log(typeof result); // "number"

Explicit Conversion

1. Convert To Number

let num = "123";
num = +num;
console.log(typeof num); // "number"
console.log(Number("10")); // 10
console.log(Number("10.5")); // 10.5
console.log(parseInt("10.5")); // 10
console.log(parseFloat("10.5")); // 10.5
console.log(Number(true)); // 1
console.log(Number(false)); // 0

2. Convert To String

let num = 123;
num = num + "";
console.log(typeof num); // "string"
console.log(String(num)); // "123"
console.log(num.toString()); // "123"

3. Convert To Boolean

console.log(Boolean(0)); // false
console.log(Boolean(1)); // true
console.log(Boolean("")); // false
console.log(Boolean("Hello")); // true
console.log(Boolean(null)); // false
console.log(Boolean(undefined)); // false

4. Convert To BigInt

let big = 123456789012345678901234567890n;
console.log(typeof big); // "bigint"

let big = BigInt(100);
console.log(big); // 100n
console.log(typeof big); // "bigint"

Note: When Conversion fails then it returns NaN.

🎯 Exercises

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