用javascript简单封装AJAX

1.创建一个AJAX引擎对象

 var CreateAjax = function () {
     var xhr = null;

     if (window.XMLHttpRequest)
     {
         //非IE游览器
         xhr=new XMLHttpRequest();
     }else
     {
         //IE游览器
         xhr = new ActiveXObject("Microsoft.XMLHTTP");
     }
     return xhr;
 };

2.创建一个全局对象

var Ajax = function (option) {
    //初始化数据
    //可选GET，POST
    var type = option.type;
    //请求地址
    var url = option.url;

    var data = option.data;
    //返回数据类型
    var dataType = option.dataType;
    //是否异步
    var async = option.async;

    var success = option.success;
    //默认为GET方式
    if(type==null){
        type = "GET";
    }
    //默认返回文本类型
    if (dataType == null) {
        dataType = "text";
    }
    if (async == null) {
        async = true;
    }
    //创建XMLHttpRequest对象
    var xhr = CreateAjax();
    //打开
    xhr.open(type, url, async);
    //发送
    if (type == "GET" || type == "get") {
        xhr.send(null);
    } else if (type == "POST" || type == "post") {
        xhr.setRequestHeader("content-type",
                    "application/x-www-form-urlencoded");
        xhr.send(data);
    }

    xhr.onreadystatechange = function () {
        if (xhr.readyState ==  && xhr.status == ) {
            if (dataType == "TEXT" || dataType == "text") {
                if (success != null) {
                    success(xhr.responseText);
                } else if (dataType == "xml" || dataType == "XML") {
                    success(xhr.responseXML);
                } else if (dataType == "json" || dataType == "JSON") {
                    success(eval("(" + xhr.responseText + ")"));
                }
            }
        }
    };

};

3.调用方式

 Ajax({
                 type: "POST",
                 url: "LoginHandler.ashx",
                 data: "userName="+userName.value+"&password="+password.value,
                 dataType:"text",

                 success: function (data) {
                     alert(data);
                 }

             });

简单了封装一下，能基本满足需求..可进行扩充