Atomics.load( ) In JavaScript

Last Updated : 20 Mar, 2018

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.load() Method

Among the Atomic Operations, there is a an inbuilt operation Atomics.load() that is used to return a value which is residing at a given position in an array.
The integer typedarray and the index of the value are passed as an argument to the function.
Atomics.load() returns the value at the given position of the array.

Syntax:

Atomics.load(typedArray, index)

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 load a value.

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

Examples of the above function are provided below.

Examples:

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

Input : arr[0] = 3; 
        Atomics.add(arr, 0, 2)
        Atomics.load(arr, 0);
Output : 5

Codes for the above function are provided below.

Code 1:

<script>
// creating a SharedArrayBuffer
var buf = new SharedArrayBuffer(25);
var arr = new Uint8Array(buf);
  
// Initialising element at zeroth position of array with 9
arr[0] = 9;
  
// Displaying the SharedArrayBuffer 
console.log(Atomics.load(arr, 0));
  
</script>

OUTPUT :

Code 2:

<script>
// creating a SharedArrayBuffer 
var buf = new SharedArrayBuffer(25);
var arr = new Uint8Array(buf);
  
// Initialising 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.add() method 
console.log(Atomics.add(arr, 0, 2));
  
// Displaying the updated SharedArrayBuffer 
console.log(Atomics.load(arr, 0));
</script>

OUTPUT :

3
3
5

Application:
Whenever we want to return a value from a specified position of an array, we use the Atomics.load() operation in JavaScript.

Let’s see a JavaScript Program :

<script>
// creating a SharedArrayBuffer 
var mybuffer = new SharedArrayBuffer(25);
var myarray = new Uint8Array(mybuffer);
  
// Initialising the element at zeroth position of array
myarray[0] = 40;
  
// Displaying the SharedArrayBuffer 
console.log(Atomics.load(myarray, 0));
</script>

Output :

Exceptions :

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

My Personal Notes

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