ajax 表单提交， 很使用的代码，收藏了

function ajaxSubmitForm(form, resultDivId) {           
var elements = form.elements;// Enumeration the form elements           
var element;           
var i;           
var postContent = "";// Form contents need to submit          
for(i=0;i<elements.length;++i) {                   
var element=elements[i];           
if(element.type=="text" || element.type=="textarea" || element.type=="hidden") {           
postContent += encodeURIComponent(element.name) + "=" + encodeURIComponent(element.value) + "&";           
}           
else if(element.type=="select-one"||element.type=="select-multiple") {           
var options=element.options,j,item;           
for(j=0;j<options.length;++j){           
item=options[j];           
if(item.selected) {                   
postContent += encodeURIComponent(element.name) + "=" + encodeURIComponent(item.value) + "&";                           
}           
}           
} else if(element.type=="checkbox"||element.type=="radio") {           
if(element.checked) {                           
postContent += encodeURIComponent(element.name) + "=" + encodeURIComponent(element.value) + "&";                        
}                 
} else if(element.type=="file") {                         
if(element.value != "") {                                 
postContent += encodeURIComponent(element.name) + "=" + encodeURIComponent(element.value) + "&";                        
}                 
} else {                                 
postContent += encodeURIComponent(element.name) + "=" + encodeURIComponent(element.value) + "&";               
}           
}           
alert(postContent);           
ajaxSubmit(form.action, form.method, postContent);           
}           
// url - the url to do submit           
// method - "get" or "post"           
// postContent - the string with values to be submited           
// resultDivId - the division of which to display result text in, in null, then           
// create an element and add it to the end of the body          
function ajaxSubmit(url, method, postContent, resultDivId)            {           
var loadingDiv = document.getElementById('loading');               
// call in new thread to allow ui to update                  
window.setTimeout(function () {                         
loadingDiv.innerText = "Loading....";                      
loadingDiv.style.display = "";             
}, 1);               
// code for Mozilla, etc.           
if (window.XMLHttpRequest)                {                         
xmlhttp=new XMLHttpRequest();            
}                 
// code for IE              
else if (window.ActiveXObject)                    {
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");                  
}                 
if(xmlhttp) {                    
xmlhttp.onreadystatechange = function() {                               
// if xmlhttp shows "loaded"                               
if (xmlhttp.readyState==4)                                   {
if(resultDivId) {                                               
document.getElementByID(resultDivId).innerHTML = xmlhttp.responseText;                                   
} else {           
var result = document.createElement("DIV");          
result.style.border="1px solid #363636";           
result.innerHTML = xmlhttp.responseText;          
document.body.appendChild(result);                                     
}                                         
loadingDiv.innerHTML = "Submit finnished!";                             
}                         
};                       
if(method.toLowerCase() == "get") {                              
xmlhttp.open("GET", url + "?" + postContent, true);                                
xmlhttp.send(null);                      
} else if(method.toLowerCase() == "post") {  
xmlhttp.open("POST", url, true);  
xmlhttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");  
xmlhttp.send(postContent);    
}           
} else {   
loadingDiv.innerHTML = "Can't create XMLHttpRequest object, please check your web browser.";   
}      
}