<script type="text/javascript">
    
      function ajax() {

          //先聲明一個(gè)異步請(qǐng)求對(duì)象
          var xmlHttpReg = null;
          if (window.ActiveXObject) {//如果是IE

              xmlHttpReg = new ActiveXObject("Microsoft.XMLHTTP");

          } else if (window.XMLHttpRequest) {

              xmlHttpReg = new XMLHttpRequest(); //實(shí)例化一個(gè)xmlHttpReg
          }

          //如果實(shí)例化成功,就調(diào)用open()方法,就開(kāi)始準(zhǔn)備向服務(wù)器發(fā)送請(qǐng)求
          if (xmlHttpReg != null) {
              xmlHttpReg.open("get", "chuli.php?uid="+uid+"&pwd="+pwd, true);
               xmlHttpReg.send(null);
              xmlHttpReg.onreadystatechange = doResult(); //設(shè)置回調(diào)函數(shù)
               
          }

          //回調(diào)函數(shù)
          //一旦readyState的值改變,將會(huì)調(diào)用這個(gè)函數(shù),readyState=4表示完成相應(yīng)

          //設(shè)定函數(shù)doResult()
          function doResult() {
          
              if (xmlHttpReg.readyState == 4) {//4代表執(zhí)行完成