Javascript拦截
拦截form 的submit

var oldSubmit;
var form = document.forms[0];
if(form != null && form != 'undefined'){
//备份submit函数
form.oldSubmit = form.submit;
//覆盖submit函数以实现拦截
form.submit = function (){
//提交前做的操作..
//掉原函数来提交
form.oldSubmit();
}
}