Concatenate then assign (+=) (Operator/assignment)

Concatenate two string operands and assign the result to the first. See Addition for numeric values.


ECMAScript edition - 2
JavaScript - 1.0
JScript - 1.0
Internet Explorer - 3.02
Netscape - 2.0
Property/method value type:Number primitive
JavaScript syntax:-anOperand1 += anOperand2
Argument list:anOperand1A numeric value that can be assigned to
anOperand2Another numeric value

Concatenate the right operand to the left operand and assign the result to the left operand.

This is functionally equivalent to the expression:

anOperand1 = anOperand1 + anOperand2;

Although this is classified as an assignment operator, it is really a compound of an assignment and a concatenation operator.

It also works with numeric values and will add the second to the first.

The associativity is right to left.

Refer to the Operator Precedence topic for details of execution order.

The new value of anOperand1 is returned as a result of the expression.


See also:Add then assign (+=), Assign value (=), Assignment expression, Assignment operator, Associativity, LValue, Operator Precedence


ECMA 262 edition 2 - section - 11.13

ECMA 262 edition 3 - section - 11.13