IE7以下不兼容JS的onsubmit方法

在测试浏览器兼容问题时，发现IE6、IE7不支持在Javascript中调用form对象的onsubmit方法，本方法用于兼容IE6、IE7下对onsubmit方法的支持，各大浏览器均测试过。

function checkIE() { // 检查IE版本号，非IE浏览器返回null
var appName = navigator.appName,
userAgent = navigator.userAgent,version,versionfloat;
if (appName == 'Microsoft Internet Explorer') {
version = /MSIE\s(\S)/.exec(userAgent)[1];
versionfloat = parseFloat(version);
return versionfloat;
}
return null;
}
function onsubmitForm(formId){// 可传入表单对象或者表单ID
var form1;
if('object'==typeof(formId) && formId.tagName=="FORM"){
form1 = formId;
}else{
form1 = document.getElementById(formId);
}
var num = checkIE(),bool=false;
if(num>7||num==null)bool = true;
if(bool){
form1.onsubmit();
}else{
var uniqId = form1.uniqueID;
var str = form1.onsubmit+'';
var reg = /^function/;
var isFunction = reg.test(str);
if(isFunction){
str = str.replace('function onsubmit()', 'function onsubmit_'+uniqId+'()');
}else{
str = 'function onsubmit_'+uniqId+'(){' + str + '}';
}
eval(str);
eval('onsubmit_'+uniqId+'()');
}
}