String.fmt

string.js

/**
 * String.fmt
 *
 * String prototype for interpolating positioned arguments into a string.
 *
 * @param {Array} args   List of strings to be inserted.
 * @return {String}
 */
String.prototype.fmt = function String_fmt() {
    var args = arguments,
        formatted = this.toString(),
        ordered = (formatted.indexOf('%@1') >= 0),
        replace;

    for (var i = 0, len = args.length; i < len; i += 1) {
        replace = (ordered) ? '%@'+(i+1) : '%@';
        formatted = formatted.replace(replace, args[i]);
    }
    return formatted;
};