javascript-ajax学习

/* *
 *     @todo 封装Ajax 传输类
 *     @param params:参数
 *    @example 用法： var mAjaxer = new Ajaxer(parames);mAjaxer.send();
  */
(function (window,undefined) {
    var defined = {},
        rtrim = /^(\s|\u00A0)+|(\s|\u00A0)+$/g;
    defined.trim = function( text ) 
    {
        return (text || "").replace( rtrim, "" );
    };
    defined.parseJSON = function(data,error) 
    {
        if ( typeof data !== "string" || !data ) 
            return null;
        data = this.trim(data);
        // Make sure the incoming data is actual JSON
        // Logic borrowed from http://json.org/json2.js
        if ( /^[\],:{}\s]*$/.test(data.replace(/\\(?:["\\\/bfnrt]|u[0-9a-fA-F]{4})/g, "@")
            .replace(/"[^"\\\n\r]*"|true|false|null|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?/g, "]")
            .replace(/(?:^|:|,)(?:\s*\[)+/g, "")) ) {
            // Try to use the native JSON parser first
            return window.JSON && window.JSON.parse ?
                window.JSON.parse( data ) :
                (new Function("return " + data))();
        }
        else 
            error("Invalid JSON: " + data);
    };
    defined.json2String = function(jsonData) {
        var strArr = [];
        for(var k in jsonData) {
            strArr.push(k + "=" + jsonData[k]);    
        }
            
        return strArr.join("&");
    }
    var Ajaxer = function(params)
    {
        var _p = {},
            xmlHttp;
        if (typeof params == ‘undefined‘) 
        {
            return false;
        }
        // 发送请求
        this.send =    function ()
        {
            xmlHttp = null;
            xmlHttp = _p.createXMLHttp();
            if(xmlHttp == null)
            {
                error = {‘code‘ : 404,"message" : "您的浏览器版本过低，无法创建异步对象，请升级您的浏览器！"}
                params.error(error);
            }
            else
            {
                //打开ajax请求
                xmlHttp.open(params.method,params.url,params.async);
                //一般jquery会传递这个参数,进行区分ajax请求
                xmlHttp.setRequestHeader("X-Requested-With","XMLHttpRequest"); 
                //如果是post的话,要对url进行encode
                if (params.method.toLowerCase() == ‘post‘)
                {
                    xmlHttp.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
                    if (typeof params.data != ‘string‘)
                        params.data = defined.json2String(params.data);
                    //对post或get发送数据
                    xmlHttp.send(params.data);
                }
                else
                {
                    xmlHttp.send(null);
                }
                
                //处理状态
                xmlHttp.onreadystatechange = _p.SendBack;
            }
        };
        //处理回调函数
        _p.SendBack = function ()
        {    
            if(xmlHttp.readyState == 4)
            {
                if(xmlHttp.status == 200)
                {    
                    var data,
                        ct = xmlHttp.getResponseHeader("content-type") || "";
                    data = xmlHttp.response;
                    //判断是否是json
                    if (params.dataType === "json" || !params.dataType && ct.indexOf("json") >= 0)
                    {
                        data = defined.parseJSON(data,params.error);
                    }
                    params.success(data);                
                }
                else
                {
                    var error = {‘code‘ : xmlHttp.status,"message" : xmlHttp.statusText};
                    params.error(error);
                }
                if (params.async) 
                {
                    xmlHttp = null;
                }
            }
        };
        //创建ajax对象
        _p.createXMLHttp = function()
        {
            var xmlhttp = null;
        
            // 针对不同浏览器建立这个对象的不同方式写不同代码
            if(window.XMLHttpRequest) {
                xmlhttp = new XMLHttpRequest();
                //针对某些特定版本的Mozillar浏览器的BUG进行修正
                if(xmlhttp.overrideMimeType) {
                    xmlhttp.overrideMimeType("text/xml");
                }
                
            } else if (window.ActiveXObject) {
                var activexName = [‘MSXML2.XMLHTTP‘, ‘Microsoft.XMLHTTP‘];
                for (var i=0; i<activexName.length; i++) {
                    try {
                        xmlhttp = new ActiveXObject(activexName[i]);
                        break;
                    } catch(e) {}
                }
            }
            return xmlhttp;
        }
    }
    
    window.Ajaxer = Ajaxer;
    window.defined = defined;
})(window);