ajax学习笔记

最近听了博客园的ajax课程做点笔记。
主要的函数：
XMLHttpRequest对象（Cont.）
􀂄方法：
􀂅void open(Stringmethod, String url, Boolean async)
􀂅void send(Stringbody)
􀂅void setHeader(Stringheader, String value)
􀂅String getResponseHeader(Stringheader)
􀂅String getAllResponseHeaders()
􀂅void abort()
XMLHttpRequest对象（Cont.）
􀂄属性：
􀂅Number readyState
􀂅Function onreadystatechange
􀂅String responseText
􀂅XmlDocumentresponseXML
􀂅Number status
􀂅String statusText
跨浏览器使用AJAX

<script language="javascript">
        var xmlHttpRequest = null;
        
        function getXMLHttpRequest()
        {
            if(window.XMLHttpRequest)
            {
                return new XMLHttpRequest();
            }
            else if (window.ActiveXObject)
            {
                request = new ActiveXObject("Microsoft.XMLHTTP");
                
                if (!request)
                {
                    request = new ActiveXObject("Msxml2.XMLHTTP");
                }
                
                return request;
            }

        }
        
        function selectionChanged()
        {
            var url = "TextHandler.ashx?index=" + document.getElementById("select").value;
            
            xmlHttpRequest = getXMLHttpRequest();
            xmlHttpRequest.onreadystatechange = onReadyStateChange;
            xmlHttpRequest.open("GET", url, true);
            xmlHttpRequest.send(null);
        }
        
        function onReadyStateChange()
        {
            if (xmlHttpRequest.readyState == 4)
            {
                if (xmlHttpRequest.status == 200)
                {
                    document.getElementById("text").innerHTML = 
                        xmlHttpRequest.responseXML.documentElement.firstChild.nodeValue;
                }
            }
        }
    </script>

错误处理
􀂄open时抛出错误
􀂅非法URL
􀂅跨域名URL
􀂄访问status时错误（没有得到正确Header）
􀂅服务器完全无法响应
􀂅URL指向不存在
􀂄status错误（不是2xx）
􀂅503 Service Unavailable
􀂅404 Not Found

<script language="javascript">
        var xmlHttpRequest = null;
        
        function getXMLHttpRequest()
        {
            if(window.XMLHttpRequest)
            {
                return new XMLHttpRequest();
            }
            else if (window.ActiveXObject)
            {
                request = new ActiveXObject("Microsoft.XMLHTTP");
                
                if (!request)
                {
                    request = new ActiveXObject("Msxml2.XMLHTTP");
                }
                
                return request;
            }

        }
        
        function start()
        {
            xmlHttpRequest = getXMLHttpRequest();
            try
            {
                xmlHttpRequest.onreadystatechange = onReadyStateChange;
                xmlHttpRequest.open("GET", url, true);
                xmlHttpRequest.send(null);
            }
            catch(e)
            {
                // invalid url
                // cross browser data access, etc.
            }
        }
        
        function onReadyStateChange()
        {
            try
            {
                if (xmlHttpRequest.readyState == 4)
                {
                    if (xmlHttpRequest.status == 200)
                    {
                        // do sth.
                    }
                    else
                    {
                        // 503 Service Unavailable
                        // 404 Not Found, etc.
                    }
                }
            }
            catch(e)
            {
                // the server host is completely down
                // the url is not correct, etc.
            }
        }
    </script>

/Files/cmzzlh/ajax-lesson1-demo.zip