Addition assignment (+=)
The addition assignment operator (+=) adds the value of the right operand
to a variable and assigns the result to the variable. The types of the two operands
determine the behavior of the addition assignment operator. Addition or concatenation is
possible.
Syntax
x += y // x = x + y
Examples
Using addition assignment
// Assuming the following variables
// foo = 'foo'
// bar = 5
// baz = true
// Number + Number -> addition
bar += 2 // 7
// Boolean + Number -> addition
baz += 1 // 2
// Boolean + Boolean -> addition
baz += false // 1
// Number + String -> concatenation
bar += 'foo' // "5foo"
// String + Boolean -> concatenation
foo += false // "foofalse"
// String + String -> concatenation
foo += 'bar' // "foobar"
Specifications
| Specification |
|---|
| ECMAScript Language Specification (ECMAScript) # sec-assignment-operators |
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