files/en-us/web/javascript/reference/global_objects/atomics/sub/index.md

metadata

title: Atomics.sub()
short-title: sub()
slug: Web/JavaScript/Reference/Global_Objects/Atomics/sub
page-type: javascript-static-method
browser-compat: javascript.builtins.Atomics.sub
sidebar: jsref

The Atomics.sub() static method subtracts a given value at a given position in the array and returns the old value at that position. This atomic operation guarantees that no other write happens until the modified value is written back.

{{InteractiveExample("JavaScript Demo: Atomics.sub()")}}

// Create a SharedArrayBuffer with a size in bytes
const buffer = new SharedArrayBuffer(16);
const uint8 = new Uint8Array(buffer);
uint8[0] = 7;

// 7 - 2 = 5
console.log(Atomics.sub(uint8, 0, 2));
// Expected output: 7

console.log(Atomics.load(uint8, 0));
// Expected output: 5

Syntax

Atomics.sub(typedArray, index, value)

Parameters

• typedArray
  • : An integer typed array. One of {{jsxref("Int8Array")}}, {{jsxref("Uint8Array")}}, {{jsxref("Int16Array")}}, {{jsxref("Uint16Array")}}, {{jsxref("Int32Array")}}, {{jsxref("Uint32Array")}}, {{jsxref("BigInt64Array")}}, or {{jsxref("BigUint64Array")}}.
• index
  • : The position in the typedArray to subtract a value from.
• value
  • : The number to subtract.

Return value

The old value at the given position (typedArray[index]).

Exceptions

• {{jsxref("TypeError")}}
  • : Thrown if typedArray is not one of the allowed integer types.
• {{jsxref("RangeError")}}
  • : Thrown if index is out of bounds in the typedArray.

Examples

Using sub

const sab = new SharedArrayBuffer(1024);
const ta = new Uint8Array(sab);
ta[0] = 48;

Atomics.sub(ta, 0, 12); // returns 48, the old value
Atomics.load(ta, 0); // 36

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also

• {{jsxref("Atomics")}}
• {{jsxref("Atomics.add()")}}