JS BigInt

JavaScript BigInt: Exact Math for Huge Integers

JavaScript BigInt represents whole integers of arbitrary size beyond Number.MAX_SAFE_INTEGER (9,007,199,254,740,991). You create a BigInt by appending n to an integer literal or calling BigInt("...") on a numeric string.

Why Number Fails on Huge Integers

Regular JavaScript numbers lose accuracy past 16 digits. For example, 9007199254740992 + 1 still evaluates to 9007199254740992 because the mantissa runs out of precision bits. That silent rounding breaks 64-bit database IDs, Snowflake tokens, and financial ledger satoshis.

BigInt solves this problem by expanding dynamically in memory to fit integers of almost any length. Comparison operators like >, <, and == still work cleanly between BigInt and Number values when checking thresholds.

Working with BigInt Safely

Notice that BigInt supports +, -, *, **, %, and integer division / (which drops fractional remainders toward zero).

// Pass huge numbers as strings to BigInt() so JS doesn't round them first
const invoiceId = BigInt("9007199254740995123");
const nextId = invoiceId + 1n;

console.log("Original:", invoiceId.toString());
console.log("Next ID: ", nextId.toString());

// Division truncates toward zero
console.log("7n / 2n =", 7n / 2n); // 3n

// Compare BigInt and Number with == or explicit conversion
console.log("Equal value:", 10n === BigInt(10)); // true

Common Mistakes to Avoid

• Mixing BigInt and Number in math: Writing 10n + 5 throws a TypeError: Cannot mix BigInt and other types. Convert one side explicitly first.
• Passing a huge literal without quotes to BigInt(): BigInt(9007199254740999) rounds the number before BigInt() receives it. Always pass "9007199254740999" as a string or write 9007199254740999n.
• Calling JSON.stringify() directly on a BigInt: JSON.stringify({ id: 10n }) throws a TypeError. Convert BigInt fields with .toString() before serializing.

Frequently Asked Questions

Can BigInt store decimal numbers?

No, BigInt supports whole integers only. Passing "3.14" to BigInt("3.14") throws a SyntaxError.

Can I pass a BigInt into Math.max() or Math.sqrt()?

No, built-in Math methods only accept regular number values and throw a TypeError when given a BigInt.

What does typeof 42n return?

It returns "bigint", which makes checking for BigInt values straightforward with typeof value === "bigint".