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();
    }
}