2.1.33 [ECMA-262/5] Section 18.104.22.168, Number.prototype.toFixed (fractionDigits)
The specification states:
An implementation is permitted to extend the behaviour of toFixed for values of fractionDigits less than 0 or greater than 20. In this case toFixed would not necessarily throw RangeError for such values.
IE9 Mode, IE10 Mode, and IE11 Mode (All Versions)
If any value of the fractionDigits function is converted to an integer and it is equal to
-∞, this value is treated as if it is the value