BigInt.asUintN()

The BigInt.asUintN static method clamps a BigInt value to the given number of bits, and returns that value as an unsigned integer.

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Syntax

BigInt.asUintN(bits, bigint);

Parameters

bits

The amount of bits available for the integer size.

bigint

The BigInt value to clamp to fit into the supplied bits.

Returns

The value of bigint modulo 2^bits, as an unsigned integer.

Description

The BigInt.asUintN method clamps a BigInt value to the given number of bits, and interprets the result as an unsigned integer. Unsigned integers have no sign bits and are always non-negative. For example, for BigInt.asUintN(4, 25n), the value 25n is clamped to 9n:

25n = 00011001 (base 2)
         ^==== Clamp to four remaining bits
===>      1001 (base 2) = 9n

Note: BigInt values are always encoded as two's complement in binary.

Examples

Staying in 64-bit ranges

The BigInt.asUintN() method can be useful to stay in the range of 64-bit arithmetic.

const max = 2n ** 64n - 1n;

BigInt.asUintN(64, max);
// ↪ 18446744073709551615n

BigInt.asUintN(64, max + 1n);
// ↪ 0n
// zero because of overflow: the lowest 64 bits are all zeros

Specifications

Specification
ECMAScript Language Specification
# sec-bigint.asuintn

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See also