/*! 
* ajax.js
* ? auth zernmal 
* @ description XMLHttpRequest and Jsonp practice
*/

function ajax(url,options ){
    
    var options = options || {} ,
        method = options.method || "GET",
        async = (typeof options.async !== "undefined") ? options.async : true ,
        user = (typeof options.user !== "undefined") ? options.user : "" ,
        pswd = (typeof options.pswd !== "undefined") ? options.pswd : "" ,
        reciveType = options.reciveType || "string" ,
        data = options.data || null ,
        header = options.header || [],
        callback = options.callback || function(){},
        xhr =  XMLHttpRequest ?  new XMLHttpRequest() : new ActiveXObject("Microsoft.XMLHTTP");

    if(method==‘GET‘ && data){
        
        var dataStr = [];

        url = (url.indexOf("?")==-1) ? url + "?" : url + "&" ; 

        for(var i in data){
            dataStr.push( i + "=" + data[i]) ;
        }
        url += dataStr.join("&");
        data = null;
    }else if(data){
        var form = new FormData();        
        for(var i in data){
            form.append( i , data[i]);    
        }
        data = form;
    }

    xhr.onreadystatechange = function() {
    
        if (xhr.readyState == 4) {// 4 = "loaded"
            if (xhr.status == 200) {// 200 = OK
                
                var responseData = null ;

                if(reciveType==="string"){
                    responseData = xhr.responseText;
                }else if(reciveType === "json"){
                    responseData = xhr.responseText;
                    
                    if( false && JSON && JSON.parse) {
                        responseData = JSON.parse(responseData);
                    }else{
                        responseData = eval(‘(‘+responseData+‘)‘);
                    }
                }

                options.callback && options.callback(responseData);
            } else {
                alert("Problem retrieving XML data");
            }
        }
    };
    
    xhr.open(method , url , async , user ,pswd);    
    
    for(var i = header.length -1 ; i > 0 ; i--){
        xhr.setRequestHeader(header[i].type, header[i].content);    
    }

    xhr.send(data);
}

function jsonp(url , options){
    var options = options || {} ,
        script = document.createElement(‘script‘) ,
        callback = options.callback || function(result){} ,
        callbackName = ‘myjsonpcall‘+ (new Date()).getTime(),
        data = options.data || {} ,
        dataStr = [];
    

    for(var i in data){
        dataStr.push( i + "=" + data[i]) ;
    }

    if(url.indexOf("?")==-1){
        url += "?"+ dataStr.join("&") +"&callback="+callbackName;
    }else{
        url += "&"+ dataStr.join("&") +"&callback="+callbackName;
    }

    script.setAttribute(‘src‘, url);    
    window[callbackName] = callback ;

    // 把script标签加入head，此时调用开始
    document.getElementsByTagName(‘head‘)[0].appendChild(script);
}

<?php

    $func = $_GET[‘func‘];

    if(function_exists($func)){
        $func();
    }else{
        funcNotExist();
    }

    function funcNotExist(){
        echo "function is not exist ! ";
    }

    function returnJson(){
        $lastName = $_GET[‘lastName‘];
        $firstName = $_GET[‘firstName‘];

        echo json_encode(array(‘firstName‘=>$firstName,‘lastName‘=>$lastName));
    }

    function returnString(){
        $lastName = $_GET[‘lastName‘];
        $firstName = $_GET[‘firstName‘];
        echo "the string you send is ".$lastName." ".$firstName;
    }

    function postReturn(){
        $lastName = $_POST[‘lastName‘];
        $firstName = $_POST[‘firstName‘];
        echo "the string you post is ".$lastName." ".$firstName;
    }

    function jsonP(){

        header(‘content-type: application/json; charset=utf-8‘);
        $lastName = $_GET[‘lastName‘];
        $firstName = $_GET[‘firstName‘];
        $callbackFunc = isset($_GET[‘callback‘])? htmlspecialchars($_GET[‘callback‘]):"callback";
        $json = json_encode(array(‘firstName‘=>$firstName,‘lastName‘=>$lastName));

        echo "$callbackFunc($json)";
    }

<!DOCTYPE html>
<html>
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <title>Ajax与Jsonp实践</title>
    <script type="text/javascript" src="js/ajax.js"></script>
</head>
<body>
<script>
    jsonp("/ajax.php?func=jsonP",{
    callback : function(result){
        console.log(result);
    },
    data : {
        lastName : "zernmal" , 
        firstName : "chen"
    } 
});


ajax("/ajax.php?func=returnJson",{
    method : "GET",
    callback : function(result){
        console.log(result);
    },
    data : {
        lastName : "zernmal" , 
        firstName : "chen"
    } ,
    reciveType : "json"
});
</script>
</body>
</html>