JavaScript URL参数解析与构建函数实现

function getParam() {
    var param = new Object()
    var item = new Array();
    if (location.search == "") {
      return param;
    };
    var query = location.search.substring(1);                                                                   
    var list = query.split('&');
    for(var i = 0; i < list.length; i++) {
      item = list[i].split('=');
      if (typeof param[item[0]] == "undefined") {
        param[item[0]] = new Array();
      }
      param[item[0]].push(item[1]);
    };
    return param;
  };

function getUrlByParam(param) {
    var url = "";
    for (field in param) {
      for (index in param[field]) {
        url += "&" + field + "=" + param[field][index];
      };
    };
    return url == "" ? url : url.substring(1);
  };