Check Even Number in JavaScript

What You’ll Learn

An even number is divisible by 2 with no remainder. This tutorial covers modulo and bitwise checks, zero and negatives, a live preview, worked JavaScript examples, edge cases, and complexity.

📝 Problem & Approach

Given an integer n, decide whether it is even (divisible by 2).

// 10  → 10 % 2 === 0  → even
// 11  → 11 % 2 === 1  → odd
// 0   → 0 % 2 === 0   → even (zero is even)

Inputs & Outputs

Minimal workflow

function isEven(n) {
  return n % 2 === 0;
}

Method comparison

🔮 Live Preview

Works with positive and negative integers in JavaScript safe range.

Press "Check parity" to classify.

Examples Gallery

Three complete JavaScript programs — modulo check, range scan, and bitwise parity. Click View Output to reveal sample console results.

function isEven(number) {
  return number % 2 === 0;
}

const number = 10;
if (isEven(number)) {
  console.log(`${number} is an even number.`);
} else {
  console.log(`${number} is not an even number.`);
}

10 is an even number.

function isEven(num) {
  return num % 2 === 0;
}

function printEvensInRange(start, end) {
  console.log(`Even numbers in the range ${start} to ${end}:`);
  let line = "";
  for (let i = start; i <= end; i++) {
    if (isEven(i)) {
      line += i + " ";
    }
  }
  console.log(line.trim());
}

printEvensInRange(1, 10);

Even numbers in the range 1 to 10:
2 4 6 8 10

function isEvenBitwise(number) {
  return (number & 1) === 0;
}

for (const n of [10, 11, 0, -4]) {
  const label = isEvenBitwise(n) ? "even" : "odd";
  console.log(`${n}: ${label}`);
}

10: even
11: odd
0: even
-4: even

🔎 Worked Walkthrough — n = 10

Trace the modulo method for a classic even value.

For contrast, 11 % 2 is 1 → odd.

⚖️ Facts Worth Knowing

Handy follow-ups interviewers sometimes ask.

🎯 Practice Problems

Try these variations to lock in the pattern.

Notes

⏱️ Time and Space Complexity

💡 Best Practices