Get the not-a-number (NaN) floating-point number as a value of type
JS_GetNaNValue returns a value of type
jsval that represents an IEEE floating-point quiet Not-a-Number (NaN).
Math.sqrt(-1) both return
NaN. So do
NaN is not equal to any other value. In fact, it is not even equal to itself: if
x is NaN, then
x != x.