# BigInt.asIntN()

## BaselineWidely 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.asIntN()` static method truncates a `BigInt` value to the given number of least significant bits and returns that value as a signed integer.

## Syntax

js
``````BigInt.asIntN(bits, bigint)
``````

### Parameters

`bits`

The amount of bits available for the returned BigInt. Should be an integer between 0 and 253 - 1, inclusive.

`bigint`

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

### Return value

The value of `bigint` modulo 2^`bits`, as a signed integer.

### Exceptions

`RangeError`

Thrown if `bits` is negative or greater than 253 - 1.

## Description

The `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 `1n`:

```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 `-7n`, because `1001` is the encoding of `-7` under two's complement:

```25n = 00011001 (base 2)
^==== Use only the four remaining bits
===>      1001 (base 2) = -7n
```

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

Unlike similar language APIs such as `Number.prototype.toExponential()`, `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.

## Examples

### Staying in 64-bit ranges

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

js
``````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
``````

## Browser compatibility

BCD tables only load in the browser