Question

Why does

[].reverse.call("string");

fails (error in both firefox and ie, returns the original string in chrome) while calling all other arrays methods on a string work ?

>>> [].splice.call("string",3)
["i", "n", "g"]
>>> [].map.call("string",function (a) {return a +a;} )
["ss", "tt", "rr", "ii", "nn", "gg"]

Answer 1

Because .reverse() modifies an Array, and strings are immutable.

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You could borrow Array.prototype.slice to convert to an Array, then reverse and join it.

var s = "string";

var s2 = [].slice.call(s).reverse().join('');

Just be aware that in older versions of IE, you can’t manipulate a string like an Array.