Assign multiple variables to the same value in JavaScript?

JavaScript allows you to assign the same value to multiple variables in a single statement using the assignment operator chaining technique.

Syntax

var variable1, variable2, variable3;
variable1 = variable2 = variable3 = value;

You can also declare and assign in one line:

var variable1 = variable2 = variable3 = value;

Example: Assigning Same Value to Multiple Variables

var first, second, third, fourth, fifth;
first = second = third = fourth = fifth = 100;

console.log("first:", first);
console.log("second:", second);
console.log("third:", third);
console.log("fourth:", fourth);
console.log("fifth:", fifth);
console.log("Sum of all values:", (first + second + third + fourth + fifth));

first: 100
second: 100
third: 100
fourth: 100
fifth: 100
Sum of all values: 500

How It Works

Assignment operators work from right to left. The expression a = b = c = 10 is evaluated as a = (b = (c = 10)), where each assignment returns the assigned value.

var x, y, z;
console.log("Assignment result:", (x = y = z = 42));
console.log("x:", x, "y:", y, "z:", z);

Assignment result: 42
x: 42 y: 42 z: 42

Using Different Variable Declaration Keywords

// With let
let a, b, c;
a = b = c = "hello";
console.log("a:", a, "b:", b, "c:", c);

// With const (declare and assign together)
const num1 = num2 = num3 = 25;
console.log("num1:", num1, "num2:", num2, "num3:", num3);

a: hello b: hello c: hello
num1: 25 num2: 25 num3: 25

Important Note About Objects and Arrays

When assigning objects or arrays, all variables point to the same reference:

var arr1, arr2, arr3;
arr1 = arr2 = arr3 = [1, 2, 3];

arr1.push(4);
console.log("arr1:", arr1);
console.log("arr2:", arr2);
console.log("arr3:", arr3);

arr1: [ 1, 2, 3, 4 ]
arr2: [ 1, 2, 3, 4 ]
arr3: [ 1, 2, 3, 4 ]

Conclusion

Use chained assignment (a = b = c = value) to assign the same value to multiple variables efficiently. Be careful with objects and arrays as they share the same reference.