JavaScript Atomics store() Method

What is Atomics?

• The Atomics is an object in JavaScript which provides the ability to perform atomic operations as static methods.
• Just like the Math object in JavaScript all the properties and methods of Atomics are also static.
• Atomics are used with SharedArrayBuffer(generic fixed-length binary data buffer) objects.
• Atomics are not constructors like other global objects.
• Atomics cannot be used with a new operator or can be invoked as a function.

Atomics Operations in JavaScript

Multiple threads can read and write the same data in memory when there shared memory is. To ensure that predicted values are written and read accurately, another operation cannot start until and unless the current one finishes. Atomic operations also cannot be interrupted.

Atomics.store() Method

• Among the Atomic Operations, there is an inbuilt operation Atomics.store() in JavaScript that is used to store a specific value at a specific position of an array.
• Atomics.store() operation returns the value which was has been stored.
• The integer typedarray, index, and the value are passed as an argument to the function and it returns the value that has been stored in the respective array.

Syntax:

Atomics.store(typedArray, index, value)

Parameters Used:

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

Return Value: Atomics.store() returns the value that has been stored.

Examples of the above function are provided below.

Examples:

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

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

Codes for the above function are provided below.

Code 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 SharedArrayBuffer 
console.log(Atomics.load(arr, 0));

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

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

Output:

9
3
3

Code 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 SharedArrayBuffer
console.log(Atomics.load(arr, 0));

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

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

Output:

3
2
2

Application:

Whenever we want to store a value at a specific position of an array and also want to return the same value, we use the Atomics.store() operation in JavaScript.

Let's see a JavaScript Program:

// creating a SharedArrayBuffer 
let mybuffer = new SharedArrayBuffer(25);
let myarray = new Uint8Array(mybuffer);

// Initializing the element at zeroth position of array
myarray[0] = 40;

// Displaying the return value of the Atomics.store() method
console.log(Atomics.store(myarray, 0, 20));

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

Output:

20
20

Exceptions:

• If the typedArray is not one of the allowed integer types then the Atomics.store( ) operation throws a TypeError.
• If the typedArray is not a shared typed array then the Atomics.store( ) operation throws a TypeError.
• If the index used as an argument to the Atomics.store( ) operation is out of the bound in the typedArray then the Atomics.store( ) operation throws a RangeError.