[Matre]

String.prototype.replaceMap = function (data) {
	var result = this;
	for (var i in data)
		if (data.hasOwnProperty(i))
			result = result.replace(new RegExp(i, "gi"), data[i]);
	return result;
};

var a = "абв";
a = a.replaceMap({
	"а" : "1",
	"б" : "2",
	"в" : "3"
});
alert(a);