js 重写全局onload、onsubmit事件

// 添加window.onload事件
function addLoadEvent(func) {
var oldonload = window.onload;
if (typeof window.onload != 'function') {
window.onload = func;
} else {
window.onload = function () {
if (oldonload) {
oldonload();
}
func();
};
}
};
// 添加form.onsubmit提交事件
function addSubmitEvent(func) {
//var oldSubmit;
var forms = document.forms;
for (var i = 0; i < forms.length; i++) {
//备份submit函数
var oldSubmit = forms[i].onsubmit;
if (typeof forms[i].onsubmit != 'function') {
forms[i].onsubmit = func;
} else {
forms[i].onsubmit = function (){
func();
//掉原函数来提交
if (oldSubmit)
oldSubmit();
return true;
}
}    
}
};