function prepareForms() {
 for(var j=0 ; j<document.forms.length ; j++){
  var this_forms = document.forms[j];
  resetFields(this_forms);
   this_forms.onsubmit = function () {
    if(!validateForm(this)) return false; //進(jìn)行瀏覽器端表單驗(yàn)證
    var article = document.getElementsByTagName("article")[0];
    if(submitFormWithAjax(this,article)) return false; //代表防止重復(fù)提交 實(shí)際的提交已經(jīng)完成
   return true;
   }
 }
}

function displayAjaxLoading(element) {
 while(element.hasChildNodes()){
  element.removeChild(element.lastChild); //如果還有子節(jié)點(diǎn) 重復(fù)刪除 直到內(nèi)部為空
 }
 var content = document.createElement("img");
 content.setAttribute("src","images/loading.gif");
 content.setAttribute("alt","loading....");
 element.appendChild(content);
} //拿到元素 清空內(nèi)部 并添加一個(gè)img
function submitFormWithAjax(whichform,thetarget) {
 var request = getHTTPObject();
 if(!request){return false ;}
 displayAjaxLoading(thetarget);//調(diào)用加載方法
 var dataParts = [];
 var element; //提前創(chuàng)建要用的容器
 for(var i=0 ; i<whichform.elements.length ; i++){
  element = whichform.elements[i];
  dataParts[i] = element.name + "=" +encodeURIComponent(element.value) //把元素的名字和值轉(zhuǎn)化成URL編碼放入容器中
 }
 var data = dataParts.join("&"); //把數(shù)組轉(zhuǎn)化成一串字符串 每個(gè)項(xiàng)目之間用&連接
 request.open("post",whichform.getAttribute("action"),true); //向表單目標(biāo)地址準(zhǔn)備提出名為post的請(qǐng)求
 request.setRequestHeader("content-type","application/x-www-form-urlencoded");//設(shè)置頭部信息
 //獲取請(qǐng)求后就會(huì)調(diào)用一下的 方法 算是一個(gè)觸發(fā)器 服務(wù)器會(huì)執(zhí)行以下內(nèi)容
 request.onreadystatechange = function () {
  if(request.readyState == 4){
   if(request.status == 200 || request.status == 0){
    var matches = request.responseText.match(/<article>([\s\S]+)<\/article>/) //捕獲文本
    if(matches.length>0){
     thetarget.innerHTML = matches[1]; //正則表達(dá)式返回0為包含<article> 1為不包含的版本
    }
    else {
     thetarget.innerHTML = "<p>sorry not find</p>";
    }
   }
   else {
    thetarget.innerHTML = "<p>" + request.statusText + "</p>";
   }
  }
 }
 request.send(data); //對(duì)目標(biāo)服務(wù)器發(fā)送請(qǐng)求
 return true;//代表函數(shù)執(zhí)行完畢
}