The operand is incremented by 1
The operand is evaluated, converted to a numeric value, and incremented by 1.
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.
ECMA 262 edition 2 - section - 11.4.4
ECMA 262 edition 2 - section - 11.6.3
ECMA 262 edition 3 - section - 11.4.4