JavaScript Atomics add() Method

Among the Atomic Operations, there is a method Atomics.add() that is used to add a given value at a given position in an array and return the old value at that position. No other write operation can happen until the modified value is written back.
Syntax: 

Atomics.add(typedArray, index, value)

Parameters: 

• typedarray: It is the shared integer typed array you want to modify.
• index: It is the position in the typedArray where you want to add a value.
• value: It is the number you want to add.

Return Value: Atomics.add() returns the old value at the given position (typedArray[index]).

Examples of the above function are provided below.

Examples: 

Input : arr[0] = 9;
        Atomics.add(arr, 0, 3);
Output : 9

Input : arr[0] = 3; 
        Atomics.add(arr, 0, 2);
Output : 3

Examples of the above function are provided below. 

Example 1: 

// creating a SharedArrayBuffer 
let buf = new SharedArrayBuffer(25);
let arr = new Uint8Array(buf);

// Initializing element at zeroth 
// position of array with 9
arr[0] = 9;

// Displaying the return value of
// the Atomics.add() method 
console.log(Atomics.add(arr, 0, 3));

// Displaying the updated SharedArrayBuffer
console.log(Atomics.load(arr, 0));

Output: 

9
12

Example 2: 

// creating a SharedArrayBuffer
let buf = new SharedArrayBuffer(25);
let arr = new Uint8Array(buf);

// Initializing element at zeroth
// position of array with 3 
arr[0] = 3;

// Displaying the return value of
// the Atomics.add() method
console.log(Atomics.add(arr, 0, 2));

// Displaying the updated SharedArrayBuffer
console.log(Atomics.load(arr, 0));

Output: 

3
5

Exceptions:

• Throws a TypeError, if typedArray is not one of the allowed integer types.
• Throws a TypeError, if typedArray is not a shared typed array type.
• Throws a RangeError, if the index is out of bounds in the typedArray.

Supported Browser:

• Google Chrome
• Internet Explorer
• Firefox
• Opera
• Safari

We have a complete list of Javascript Atomic methods, to check those please go through this JavaScript Atomics Complete Reference article.

We have a Cheat Sheet on Javascript where we covered all the important topics of Javascript to check those please go through Javascript Cheat Sheet-A Basic guide to JavaScript.