SpiderMonkey supports larger range in toFixed, toPrecision, toExponential see revision 29020 JavaScriptCore vs. SpiderMonekey: toFixed: 0 to 20 vs. -20 to 100 toPrecision: 1 to 21 vs. 1 to 100 toExponential: 0 to 20 vs. -20 to 100 Our support agrees with the Ecma spec. Mozilla just decided to be over-achievers.
I don't think we plan on going beyond the spec here. In absence of real world compatibility concerns, closing.