String format in JavaScript

string_format.js

String.prototype.format = function () {
    var g = this.toString();
    if (!arguments.length) return g;
    var c = "string" == typeof arguments[0] ? arguments : arguments[0],
        e;
    for (e in c) g = g.replace(RegExp("\\{" + e + "\\}", "gi"), c[e]);
    return g
};