The operand is evaluated and converted to a numeric value. The result is negated.

A positive value becomes negative and a negative value becomes positive.

This is functionally equivalent to:

anOperand *= -1

Which is equivalent to:

anOperand = anOperand * -1

And also:

anOperand = 0 - anOperand

Although this is classified as a unary operator, its functionality is really that of an additive operator.

The associativity is from right to left.

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

Cross-references:

ECMA 262 edition 2 - section - 11.4.7

ECMA 262 edition 3 - section - 11.4.7