JS Selector Class

"use strict";

function Selector(sel) {
    this.valid = true;
    this.header = "@a";
    this.args = {};

    {
        if(typeof sel != "string") {this.valid = false;return null};
        var validHeaders = ["@a","@p","@e","@r"];
        if(validHeaders.indexOf(sel.substring(0,2)) > -1) {
            this.header = sel.substring(0,2);
        } else {this.valid = false;return null;}

        sel = sel.substring(2);

        var tempArgs = {};

        var token = "";
        var key = "";
        var argsCount = 0;

        var action = "GET_KEY";

        iteration: for(var i = 0; i < sel.length; i++) {
            var c = sel.charAt(i);

            if(i == 0) {
                if(c != "[") break; else continue;
            }

            if("]=, ".indexOf(c) > -1) {
                switch(c) {
                    case "]":
                    case ",": {
                        if(action == "GET_KEY" && token.length > 0) {
                            key = ["x","y","z","r"][argsCount];
                            if(key == undefined) {
                                break iteration;
                            }
                            tempArgs[key] = token;
                            token = key = "";
                            argsCount++;
                            break;
                        } else if(action == "GET_VALUE") {
                            tempArgs[key] = token;
                            token = key = "";
                            action = "GET_KEY";
                            argsCount++;
                            break;
                        }
                        if(c == "]") {
                            break iteration;
                        }
                    }
                    case "=": {
                        if(action == "GET_KEY") {
                            key = token;
                            token = "";
                            action = "GET_VALUE";
                            break;
                        } else if(action == "GET_VALUE") {
                            break iteration;
                        }
                    } case " ": {
                        break iteration;
                    }
                }
            } else {
                token += c;
            }

        }
        this.args = tempArgs;
    }

    this.clone = function() {
        var ns = new Selector();
        ns.valid = this.valid;
        ns.header = this.header;
        ns.args = {};
        for(var i  in this.args) {
            ns.args[i] = this.args[i];
        }
        return ns;
    }
}

Selector.prototype.toString = function() {
    if(!this.valid) return null;
    var s = this.header;
    var hasArgs = false;
    var argsRaw = "";

    for(var i in this.args) {
        hasArgs = true;
        argsRaw += i + "=" + this.args[i] + ",";
    }
    if(argsRaw.charAt(argsRaw.length-1) == ",") argsRaw = argsRaw.substring(0,argsRaw.length-1);

    s += (hasArgs) ? ("[" + argsRaw + "]") : "";
    return s;
}