JAVASCRIPT判断一个值或者控件是否为NULL,null,undefined,""的方法 转载自:http://www.cnblogs.com/kaixin110/archive/2008/03/13/1103694.html Code1var vehicleid = $F('desAutos');2 if(vehicleid == null || vehicleid == undefined || (!vehicleid) )3 {4 window.alert("请输入目标车辆");5 return;6 }