What's the Math.sign() Alternative for BigInt Values in JavaScript?

The JavaScript Math.sign() method only works on the number primitive values, and not on the bigint primitive values:

// TypeError: Cannot convert a BigInt value to a number

Therefore, you can implement a custom "sign" method for bigint numbers instead, which would return similar values to the Math.sign() method, i.e.:

  • Return 0 if value is 0;
  • Return -0 if value is -0;
  • Return 1 if value is greater than 0;
  • Return -1 if value is less than 0.

You can implement this for bigint numbers in the following way:

// ES10+
const sign = (val) => {
    if (val === 0n) {
        return val;

    return (val < 0n) ? -1n : 1n;

Please note that if the value is -0n, then 0n is returned (instead of -0n). This is due to the way browsers handle the -0n as a return value.

For example, you could use the custom sign function (with bigint values) in the following way:

console.log(sign(0n)); // 0n
console.log(sign(-0n)); // 0n
console.log(sign(10n)); // 1n
console.log(sign(-10n)); // -1n
console.log(sign(18014398509481982n)); // 1n
console.log(sign(-18014398509481982n)); // -1n
console.log(sign(BigInt(Number.MAX_SAFE_INTEGER))); // 1n
console.log(sign(BigInt(-Number.MAX_SAFE_INTEGER))); // -1n

This post was published by Daniyal Hamid. Daniyal currently works as the Head of Engineering in Germany and has 20+ years of experience in software engineering, design and marketing. Please show your love and support by sharing this post.