BigInt.asUintN()

¥Syntax

BigInt.asUintN(bits, bigint)

¥Parameters

bits

返回的 BigInt 可用的位数。应为 0 到 2 之间的整数⁵³ - 1、包容性。

bigint

要截断以适合提供的位的 BigInt 值。

¥Return value

bigint 模 2^bits 的值，为无符号整数。

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

¥Exceptions

RangeError

如果 bits 为负数或大于 2⁵³，则抛出该异常 - 1.

¥Description

BigInt.asUintN 方法将 BigInt 值截断为给定位数，并将结果解释为无符号整数。无符号整数没有符号位并且始终为非负数。例如，对于 BigInt.asUintN(4, 25n)，值 25n 被截断为 9n：

¥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

注意：BigInt 值始终编码为二进制补码。

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

与 Number.prototype.toExponential() 等类似语言 API 不同，asUintN 是 BigInt 的静态属性，因此你始终将其用作 BigInt.asUintN()，而不是用作 BigInt 值的方法。将 asUintN() 暴露为 "标准库函数" 允许 与 asm.js 互操作。

¥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

BigInt.asUintN() 方法对于保持在 64 位算术范围内非常有用。

¥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

¥See also

• BigInt
• BigInt.asIntN()