BigInt.asIntN() static method truncates a
BigInt value to the given number of least significant bits and returns that value as a signed integer.
The amount of bits available for the returned BigInt. Should be an integer between 0 and 253 - 1, inclusive.
The BigInt value to truncate to fit into the supplied bits.
The value of
bigint modulo 2^
bits, as a signed integer.
bitsis negative or greater than 253 - 1.
BigInt.asIntN method truncates a
BigInt value to the given number of bits, and interprets the result as a signed integer. For example, for
BigInt.asIntN(3, 25n), the value
25n is truncated to
25n = 00011001 (base 2) ^=== Use only the three remaining bits ===> 001 (base 2) = 1n
If the leading bit of the remaining number is
1, the result is negative. For example,
BigInt.asIntN(4, 25n) yields
1001 is the encoding of
-7 under two's complement:
25n = 00011001 (base 2) ^==== Use only the four remaining bits ===> 1001 (base 2) = -7n
BigInt values are always encoded as two's complement in binary.
Unlike similar language APIs such as
asIntN is a static property of
BigInt, so you always use it as
BigInt.asIntN(), rather than as a method of a BigInt value. Exposing
asIntN() as a "standard library function" allows interop with asm.js.
Staying in 64-bit ranges
BigInt.asIntN() method can be useful to stay in the range of 64-bit arithmetic.
const max = 2n ** (64n - 1n) - 1n; BigInt.asIntN(64, max); // 9223372036854775807n BigInt.asIntN(64, max + 1n); // -9223372036854775808n // negative because the 64th bit of 2^63 is 1
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