Web/JavaScript/Reference/Operators/Subtraction assignment

The subtraction assignment operator (-=) subtracts the value of the right operand from a variable and assigns the result to the variable.

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Syntax

Operator: x -= y
Meaning:  x  = x - y

Examples

Using subtraction assignment

// Assuming the following variable
//  bar = 5

bar -= 2     // 3
bar -= 'foo' // NaN

Specifications

Specification

ECMAScript (ECMA-262)The definition of 'Assignment operators' in that specification.

Browser compatibility

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See also

• Assignment operators in the JS guide
• Subtraction operator

Subtraction assignment (-=) by Mozilla Contributors is licensed under CC-BY-SA 2.5.