Addition Assignment (+=) Operator in Javascript

JavaScript Addition assignment operator(+=) adds a value to a variable, The Addition Assignment (+ =) Sums up left and right operand values and then assigns the result to the left operand. The two major operations that can be performed using this operator are the addition of numbers and the concatenation of strings.

Syntax:

a += b 

Example 1: In this example, we will concatenate two numbers as well as two strings by using the Addition Assignment operator(+=)

//concatenation of two number
let x = 2;
let y = 5;
console.log(x += y);

//concatenation of two string
let a = 'Geeks'
let b = 'forGeeks'
console.log(a += b);

Output: When the operator is used on a number addition is performed and concatenation is performed on strings

7
GeeksforGeeks

Example 2: Here with the help of for..in  loop, we use the Additional assignment operator.

let cities = ["Delhi", "Noida", "Dehradun", "Haldwani", "Haridwar"];
let start_with_D = " ";
for (city in cities) {
    if (cities[city].startsWith("D")) {
        let names = cities[city] + " ";
        start_with_D += names
    }
}

console.log(start_with_D);

Output: Here we use an operator to add filtered content to a string

Delhi Dehradun

Supported browser:

• Google Chrome
• Mozilla Firefox
• Safari
• Internet Explorer

We have a complete list of Javascript Assignment operators, to check those please go through the JavaScript Assignment operators article.