AJAX学习笔记

var xmlhttp;
if (window.XMLHttpRequest)
{
    //  IE7+, Firefox, Chrome, Opera, Safari 浏览器执行代码
    xmlhttp=new XMLHttpRequest();
}
else
{
    // IE6, IE5 浏览器执行代码
    xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}

xmlhttp.open("POST","/try/ajax/demo_post2.php",true);
xmlhttp.setRequestHeader("Content-type","application/x-www-form-urlencoded");//常用有两种：application/x-www-form-urlencoded和multipart/form-data
xmlhttp.send("fname=Henry&lname=Ford");//这里发送表单的数据

<input type="text" id="txt1" onkeyup="showHint(this.value)" />

function showHint(str)
{
var xmlhttp;
if (str.length==0)
  { 
  document.getElementById("txtHint").innerHTML="";//设置空白
  return;
  }
....
xmlhttp.onreadystatechange=function()  //onreadystatechange 事件
  {
  if (xmlhttp.readyState==4 && xmlhttp.status==200)
    {
    document.getElementById("txtHint").innerHTML=xmlhttp.responseText;
    }
  }
xmlhttp.open("GET","/ajax/gethint.asp?q="+str,true);
xmlhttp.send();

document.getElementById("txtHint").innerHTML=xmlhttp.responseText;

function loadDoc() {
  var xhttp = new XMLHttpRequest();
  xhttp.onreadystatechange = function() {
    if (this.readyState == 4 && this.status == 200) {
    myFunction(this);
    }
  };
  xhttp.open("GET", "cd_catalog.xml", true);
  xhttp.send();
}
function myFunction(xml) {
  var i;
  var xmlDoc = xml.responseXML;
  var table="<tr><th>Artist</th><th>Title</th></tr>";
  var x = xmlDoc.getElementsByTagName("CD");
  for (i = 0; i <x.length; i++) { 
    table += "<tr><td>" +
    x[i].getElementsByTagName("ARTIST")[0].childNodes[0].nodeValue +
    "</td><td>" +
    x[i].getElementsByTagName("TITLE")[0].childNodes[0].nodeValue +
    "</td></tr>";
  }
  document.getElementById("demo").innerHTML = table;
}