JavaScript - Safe Assignment Operator

JavaScriptSafe Assignment Operator (?=)is a suggested new feature for JavaScript that makes it easier to handle errors in code. This operator helps developers deal with errors more simply, without having to use complicated try/catch blocks.

It is denoted by(?=)symbol. It is currently under development and not yet part of the official ECMAScript specification.

Syntax

The syntax for using the Safe Assignment Operator is as follows.

variable ?= value;

Examples

Here are the simple and examples of usingsafe assignment operatorthat will help to better understand it:

Using Safe Assignment Operator

This example demonstrates how to use the operator to assign a value only if the variable is currently null or undefined.

// Initial variable set to null

let username = null;



// Using the Safe Assignment Operator

// to assign a default value

username ?= "Guest";



// Alerting the result

alert(username); // This will alert "Guest"

Output

The variable username is set as null. The lineusername ?= “Guest”;checks if it’s null or undefined and sets it to”Guest”. Finally,alert(username);shows that username is now”Guest”.

Guest

Assign a Calculated Value

This example demonstrates how to use the operator to assign a calculated value only if the variable is currently null or undefined.

// Function to perform a simple calculation

function calculate(value) {

    return value * 2; // Simple calculation: double the input

}



// Initial variable set to null

let result = null;



// Using the Safe Assignment Operator to assign the calculated value

result ?= calculate(5); // Assigns 10 if result is null



// Alerting the result

alert(result); // This will alert "10"

Output

Thecalculatefunction takes a number and returns its double. The variable result is set asnull. The lineresult ?= calculate(5);checks if result is “null”, and since it is, it callscalculate(5), which returns10and assigns it to result. Finally,alert(result);shows that result is now10.

10

This operator is supported by modern browsers (Chrome 91+, Firefox 89+, Edge 91+, Safari 15+) and Node.js (14.17.0+)