minimustache.js

String.prototype.format = function() {
    var formatted = this;
    var arg = arguments[0];
    var regexp = null;
    var key = null;
    if(arg === Object(arg) && arg instanceof Array !== true) {
        for(key in arg) {
            if(arg.hasOwnProperty(key)) {
                regexp = new RegExp('\\{{' + key + '\\}}', 'gi');
                formatted = formatted.replace(regexp, arg[key]);
            }
        }
    } else {
        for (var i = 0; i < arguments.length; i++) {
            var regexp = new RegExp('\\{{' + i + '\\}}', 'gi');
            formatted = formatted.replace(regexp, arguments[i]);
        }
    }
    return formatted;
};