Swap Two Numbers in JavaScript

What You’ll Learn

Swapping exchanges two variables so each holds the other’s old value: a=5, b=10 becomes a=10, b=5. You will use a temp variable, JavaScript’s [a, b] = [b, a], and an optional XOR trick for integers — plus a live preview and worked examples.

📝 Problem & Approach

Given two variables, exchange their values so each holds what the other used to hold.

# Before: a = 5,  b = 10
# After:  a = 10, b = 5

Inputs & Outputs

Minimal workflow

temp = a
a = b
b = temp

Method comparison

🔮 Live Preview

Enter two integers and swap them with a temporary variable.

Press “Swap”.

Examples Gallery

Three complete JavaScript programs — temp variable, destructuring, and XOR for integers. Click View Output to reveal sample console results.

let num1 = 5;
let num2 = 10;

console.log(`Before swapping: num1 = ${num1}, num2 = ${num2}`);
const temp = num1;
num1 = num2;
num2 = temp;
console.log(`After swapping: num1 = ${num1}, num2 = ${num2}`);

Before swapping: num1 = 5, num2 = 10
After swapping: num1 = 10, num2 = 5

let num1 = 5;
let num2 = 10;

console.log(`Before swapping: num1 = ${num1}, num2 = ${num2}`);
[num1, num2] = [num2, num1];
console.log(`After swapping: num1 = ${num1}, num2 = ${num2}`);

Before swapping: num1 = 5, num2 = 10
After swapping: num1 = 10, num2 = 5

let a = 5;
let b = 10;

if (a !== b) {
  a ^= b;
  b ^= a;
  a ^= b;
}

console.log(`After swapping: a = ${a}, b = ${b}`);

After swapping: a = 10, b = 5

🔎 Worked Walkthrough — 5 and 10

Follow the temp variable through each assignment.

If you assign a = b first without saving, the original 5 disappears.

⚖️ Facts Worth Knowing

Handy follow-ups interviewers sometimes ask.

🎯 Practice Problems

Try these variations to lock in the pattern.

Notes

⏱️ Time and Space Complexity

Swapping two variables does a fixed number of assignments regardless of the values.

💡 Best Practices