Last Updated : 23 Jul, 2025
This is a new operator introduced by javascript. This operator is represented by x ??= y and it is called Logical nullish assignment operator. Only if the value of x is nullish then the value of y will be assigned to x that means if the value of x is null or undefined then the value of y will be assigned to x.
Let's discuss how this logical nullish assignment operator works. Firstly we all know that logical nullish assignment is represented as x ??= y, this is derived by two operators nullish coalescing operator and assignment operator we can also write it as x ?? (x = y). Now javascript checks the x first, if it is nullish then the value of y will be assigned to x.
Syntax :
x ??= y // Means : x ?? (x = y)
Example 1 :
JavaScript
let x = 12;
let y = null;
let z = 13;
// The value of x will become
// unchanged because x is not nullish.
x ??= z;
// The value of y will be
// changed because y is nullish.
y ??= z;
console.log(x) // 12
console.log(y) // 13
Output :
12 13
Example 2 :
JavaScript
let x = {
name : "Ram"
}
// The value of name will remain
// unchanged because x.name is not nullish
x.name ??= "Shyam";
// There is no any property named age in object x .
// So the value of x.age will be
// undefined and undefined means nullish.
// that's why the value of age will be assigned.
x.age ??= 18;
console.log(x.name) // Ram
console.log(x.age) // 18
Output :
"Ram" 18
Example 3:
HTML
<h1>Hello Geeksforgeeks</h1>
<p id="print_arr"></p>
<script>
let arr = [1, 2, "apple", null, undefined, []]
// Replace each nullish values with "gfg"
arr.forEach((item, index)=>{
arr[index] ??= "gfg"
})
document.getElementById("print_arr")
.innerText = arr.toString();
//console.log(arr)
</script>
Output :
Supported browsers
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HTML:
3.2
| Encoding:
UTF-8
| Version:
0.7.4