Extend the String superclass to enable a more OO-elegant way of joining strings.

concat.String.js

(function(){
    String.prototype.concat = function(argument){
        if ( arguments.length > 0 ){
            if ( typeof argument === "string" ) {
                return this + argument;
            } else {
                var str = "";
                for ( var i in argument ){
                    str += argument[i];
                }
                return this + str;
            }
        }
        return this;
    };
})();

console.log("foo".concat("bar"));
console.log("Hello".concat([" World", "!"]));