BigInt.asUintN()
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since September 2020.
The BigInt.asUintN()
static method truncates a BigInt
value to the given number of least significant bits and returns that value as an unsigned integer.
Try it
Syntax
BigInt.asUintN(bits, bigint)
Parameters
Return value
The value of bigint
modulo 2^bits
, as an unsigned integer.
Exceptions
RangeError
-
Thrown if
bits
is negative or greater than 253 - 1.
Description
The BigInt.asUintN
method truncates 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 truncated to 9n
:
25n = 00011001 (base 2) ^==== Use only the four remaining bits ===> 1001 (base 2) = 9n
Note: BigInt
values are always encoded as two's complement in binary.
Unlike similar language APIs such as Number.prototype.toExponential()
, asUintN
is a static property of BigInt
, so you always use it as BigInt.asUintN()
, rather than as a method of a BigInt value. Exposing asUintN()
as a "standard library function" allows interop with asm.js.
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 |
Browser compatibility
BCD tables only load in the browser