want to implement layui multi-selection drop-down box
 var select = $(this)
                            ,title = reElem.find("." + TITLE)
                            ,input = title.find("input")
                            ,multiSelect = title.find(".multiSelect")
                            ,dl = reElem.find("dl:eq(0)")
                            ,dds = dl.find("div>dd").length==0 ? dl.find("dd") : dl.find("div>dd")
                            ,index =  this.selectedIndex //
                            ,nearElem //select 
                            ,omit = typeof select.attr("lay-omit") === "undefined" //  x
                            ,isMulti = typeof select.attr("multiple") && typeof select.attr("multiple") === "string";
                        that.hidePlaceholder(title,select);
                        if(disabled) return;this is a part of the form source code that has not been changed.
