Subtracts the value of an expression from the value of a variable and assigns the result to the variable.
Syntax
result -= expression
Parameters
result
Any numeric variable.
expression
Any numeric expression.
Remarks
Using the -= operator is exactly the same as doing the following:
result = result - expression
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
Subtraction Operator (-)
Operator Precedence
Operator Summary (JavaScript)