Assignment
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JavaScript Assignment
Assignment operators assign values to JavaScript variables. While the basic assignment is the most frequent, compound operators make code more concise and readable.
1. Basic Assignment (=)
The simple assignment operator (
=) assigns a value to a variable.let x = 10;2. Compound Assignment Operators
Compound operators combine an arithmetic operation with an assignment. They are shorthand for common logic.
| Operator | Example | Equivalent |
|---|---|---|
+= | x += y | x = x + y |
-= | x -= y | x = x - y |
*= | x *= y | x = x * y |
/= | x /= y | x = x / y |
%= | x %= y | x = x % y |
**= | x **= y | x = x ** y |
let x = 10;
x += 5; // x is now 153. Logical Assignment Operators
ES2021 introduced logical assignment operators, which are widely accepted in modern 2026 environments for clean state management.
OR Assignment Operator (||=)
Assigns a value to a variable if the variable is falsy.
let x = 0;
x ||= 5; // x is now 5 (because 0 is falsy)AND Assignment Operator (&&=)
Assigns a value to a variable if the variable is truthy.
let x = 10;
x &&= 5; // x is now 5 (because 10 is truthy)Nullish Coalescing Assignment (??=)
Assigns a value to a variable if the variable is null or undefined.
let x = null;
x ??= 5; // x is now 54. Bitwise Assignment
While less common in web applications, bitwise assignment operators (like
&=, |=, ^=) are used for low-level performance optimization on binary data.Top Interview Questions
?Interview Question
Q:What is the result of x += 5 if x started as 10?
A:
The result is 15. The += operator adds 5 to the current value of x (10) and then assigns that result (15) back to x.
?Interview Question
Q:How does the ??= operator work?
A:
The Nullish Coalescing Assignment operator (??=) assigns a value only if the variable is currently null or undefined. If the variable is 0 or an empty string (which are falsy but not nullish), it will NOT perform the assignment.
?Interview Question
Q:Which operator is shorthand for x = x * y?
A:
The multiplication assignment operator (*=) is used as shorthand for x = x * y.
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