Adds the value of an expression to the value of a variable and assigns the result to the variable.
Syntax
result += expression
Parameters
result
Any variable.
expression
Any expression.
Remarks
Using this operator is exactly the same as specifying: result = result + expression.
The types of the two expressions determine the behavior of the += operator.
| If | Then |
|---|---|
| Both expressions are numeric or Boolean | Add |
| Both expressions are strings | Concatenate |
| One expression is numeric and the other is a string | Concatenate |
Requirements
Supported in the following document modes: Quirks, Internet Explorer 6 standards, Internet Explorer 7 standards, Internet Explorer 8 standards, Internet Explorer 9 standards, Internet Explorer 10 standards, Internet Explorer 11 standards. Also supported in Store apps (Windows 8 and Windows Phone 8.1). See Version Information.
See Also
Addition Operator (+)
Operator Precedence
Operator Summary (JavaScript)