{
var r20 = /%20/g,            //全部空格
    rbracket = /\[\]$/,     //结尾位置匹配中括号
    rCRLF = /\r?\n/g,
    rsubmitterTypes = /^(?:submit|button|image|reset|file)$/i,
    rsubmittable = /^(?:input|select|textarea|keygen)/i;

jQuery.fn.extend({
    serialize: function() {
        return jQuery.param( this.serializeArray() );
    },
    //    console.log($(‘#form1‘).serializeArray());//[{‘name‘:‘a‘,‘value‘:‘1‘},{‘name‘:‘b‘,‘value‘:‘2‘}]
    serializeArray: function() {
        return this.map(function(){//map是数组都执行函数，返回结果集合
            //只有表单有elements属性。
            var elements = jQuery.prop( this, "elements" );
            return elements ? jQuery.makeArray( elements ) : this;
        })
        .filter(function(){
            var type = this.type;
            // Use .is(":disabled") so that fieldset[disabled] works
            return this.name && !jQuery( this ).is( ":disabled" ) &&
                rsubmittable.test( this.nodeName ) && !rsubmitterTypes.test( type ) &&
                ( this.checked || !manipulation_rcheckableType.test( type ) );
        })
        .map(function( i, elem ){
            var val = jQuery( this ).val();

            return val == null ?
                null :
                jQuery.isArray( val ) ?
                    jQuery.map( val, function( val ){
                        return { name: elem.name, value: val.replace( rCRLF, "\r\n" ) };
                    }) :
                    { name: elem.name, value: val.replace( rCRLF, "\r\n" ) };
        }).get();
    }
});

//json对象、数组对象序列化成字符串
//$.param( [ {‘name‘:1,‘value‘:2} ] );//1=2,name为key,value为value
jQuery.param = function( a, traditional ) {
    var prefix,
        s = [],
        //定义一个函数
        add = function( key, value ) {
            //是函数就让函数执行，得到返回值
            value = http://www.mamicode.com/jQuery.isFunction( value ) ? value() : ( value == null ? "" : value );
            //编码
            s[ s.length ] = encodeURIComponent( key ) + "=" + encodeURIComponent( value );
        };

    // Set traditional to true for jQuery <= 1.3.2 behavior.
    if ( traditional === undefined ) {
        traditional = jQuery.ajaxSettings && jQuery.ajaxSettings.traditional;
    }

    /*
    var $a = $(  [ {‘name‘:1,‘value‘:2},{‘name‘:3,‘value‘:4} ] )};    
    console.log( $.param($a) )
    */
    if ( jQuery.isArray( a ) || ( a.jquery && !jQuery.isPlainObject( a ) ) ) {
        // Serialize the form elements
        jQuery.each( a, function() {
            add( this.name, this.value );//每一个a的name和value属性，
        });

    } else {
        // a={‘name‘:[1,3],‘value‘:2}，a={‘name‘:{‘a1‘:1,‘a3‘:3},‘value‘:2}   add是回调进行拼接
        for ( prefix in a ) {
            buildParams( prefix, a[ prefix ], traditional, add );
        }
    }

    // 通过&链接，
    return s.join( "&" ).replace( r20, "+" );
};

//buildParams（name，[1,3]，traditional,add()）
////buildParams（name，{‘a1‘:1,‘a3‘:3}，traditional,add()）
function buildParams( prefix, obj, traditional, add ) {
    var name;

    if ( jQuery.isArray( obj ) ) {
        jQuery.each( obj, function( i, v ) {
            if ( traditional || rbracket.test( prefix ) ) {//传统方式
                add( prefix, v );

            } else {
                // 多用三目运算符
                buildParams( prefix + "[" + ( typeof v === "object" ? i : "" ) + "]", v, traditional, add );
            }
        });

    } else if ( !traditional && jQuery.type( obj ) === "object" ) {
        // Serialize object item.
        for ( name in obj ) {
            buildParams( prefix + "[" + name + "]", obj[ name ], traditional, add );
        }

    } else {
        // 不是数组不是对象，普通方式
        add( prefix, obj );
    }
}



var
    // Document location
    ajaxLocParts,
    ajaxLocation,

    ajax_nonce = jQuery.now(),

    ajax_rquery = /\?/,
    rhash = /#.*$/,
    rts = /([?&])_=[^&]*/,
    rheaders = /^(.*?):[ \t]*([^\r\n]*)$/mg,
    // #7653, #8125, #8152: local protocol detection
    rlocalProtocol = /^(?:about|app|app-storage|.+-extension|file|res|widget):$/,
    rnoContent = /^(?:GET|HEAD)$/,
    rprotocol = /^\/\//,
    rurl = /^([\w.+-]+:)(?:\/\/([^\/?#:]*)(?::(\d+)|)|)/,

    // Keep a copy of the old load method
    _load = jQuery.fn.load,

    /* Prefilters
     * 1) They are useful to introduce custom dataTypes (see ajax/jsonp.js for an example)
     * 2) These are called:
     *    - BEFORE asking for a transport
     *    - AFTER param serialization (s.data is a string if s.processData is true)
     * 3) key is the dataType
     * 4) the catchall symbol "*" can be used
     * 5) execution will start with transport dataType and THEN continue down to "*" if needed
     */
     //预过滤器，在发送ajax之前做一些处理
    prefilters = {},

    /* Transports bindings
     * 1) key is the dataType
     * 2) the catchall symbol "*" can be used
     * 3) selection will start with transport dataType and THEN go to "*" if needed
     */
     //分发器，
    transports = {},

    // Avoid comment-prolog char sequence (#10098); must appease lint and evade compression
    allTypes = "*/".concat("*");

// #8138, IE may throw an exception when accessing
// a field from window.location if document.domain has been set
try {
    ajaxLocation = location.href;
} catch( e ) {
    // 兼容性，动态创建a标签，a标签的href是空，然后就可以获取当前页面地址
    ajaxLocation = document.createElement( "a" );
    ajaxLocation.href = "";
    ajaxLocation = ajaxLocation.href;
}

// Segment location into parts
ajaxLocParts = rurl.exec( ajaxLocation.toLowerCase() ) || [];

// Base "constructor" for jQuery.ajaxPrefilter and jQuery.ajaxTransport
function addToPrefiltersOrTransports( structure ) {

    // dataTypeExpression is optional and defaults to "*"
    return function( dataTypeExpression, func ) {

        if ( typeof dataTypeExpression !== "string" ) {
            func = dataTypeExpression;
            dataTypeExpression = "*";
        }

        var dataType,
            i = 0,
            dataTypes = dataTypeExpression.toLowerCase().match( core_rnotwhite ) || [];

        if ( jQuery.isFunction( func ) ) {
            // For each dataType in the dataTypeExpression
            while ( (dataType = dataTypes[i++]) ) {
                // Prepend if requested
                if ( dataType[0] === "+" ) {
                    dataType = dataType.slice( 1 ) || "*";
                    (structure[ dataType ] = structure[ dataType ] || []).unshift( func );

                // Otherwise append
                } else {
                    (structure[ dataType ] = structure[ dataType ] || []).push( func );
                }
            }
        }
    };
}

// Base inspection function for prefilters and transports
function inspectPrefiltersOrTransports( structure, options, originalOptions, jqXHR ) {

    var inspected = {},
        seekingTransport = ( structure === transports );

    function inspect( dataType ) {
        var selected;
        inspected[ dataType ] = true;
        jQuery.each( structure[ dataType ] || [], function( _, prefilterOrFactory ) {
            var dataTypeOrTransport = prefilterOrFactory( options, originalOptions, jqXHR );
            if( typeof dataTypeOrTransport === "string" && !seekingTransport && !inspected[ dataTypeOrTransport ] ) {
                options.dataTypes.unshift( dataTypeOrTransport );
                inspect( dataTypeOrTransport );
                return false;
            } else if ( seekingTransport ) {
                return !( selected = dataTypeOrTransport );
            }
        });
        return selected;
    }

    return inspect( options.dataTypes[ 0 ] ) || !inspected[ "*" ] && inspect( "*" );
}

// 继承
function ajaxExtend( target, src ) {
    var key, deep,
        flatOptions = jQuery.ajaxSettings.flatOptions || {};

    for ( key in src ) {
        if ( src[ key ] !== undefined ) {
            ( flatOptions[ key ] ? target : ( deep || (deep = {}) ) )[ key ] = src[ key ];
        }
    }
    if ( deep ) {
        jQuery.extend( true, target, deep );
    }

    return target;
}

//    $(‘#div1‘).load("1.html ol,{‘name‘:‘hello‘}",function(a,b,c){})
jQuery.fn.load = function( url, params, callback ) {
    if ( typeof url !== "string" && _load ) {
        return _load.apply( this, arguments );
    }

    var selector, type, response,
        self = this,
        off = url.indexOf(" ");

    if ( off >= 0 ) {
        selector = url.slice( off );
        url = url.slice( 0, off );
    }

    // If it‘s a function
    if ( jQuery.isFunction( params ) ) {

        // We assume that it‘s the callback
        callback = params;
        params = undefined;

    // Otherwise, build a param string
    } else if ( params && typeof params === "object" ) {
        type = "POST";//对象是post方式
    }

    // If we have elements to modify, make the request
    if ( self.length > 0 ) {
        jQuery.ajax({
            url: url,
            type: type,//默认是get
            dataType: "html",//返回数据类型
            data: params //传输数据
        }).done(function( responseText ) {//responseText返回的数据
            response = arguments;
    //self.html()添加到本元素的html内容中
            self.html( selector ? //有过滤器

                //动态创建div,添加返回的html,查找过滤器
                jQuery("<div>").append( jQuery.parseHTML( responseText ) ).find( selector ) :

                // Otherwise use the full result
                responseText );
//complete是完成不管成功失败
        }).complete( callback && function( jqXHR, status ) {
            self.each( callback, response || [ jqXHR.responseText, status, jqXHR ] );
        });
    }

    return this;
};

// Attach a bunch of functions for handling common AJAX events
jQuery.each( [ "ajaxStart", "ajaxStop", "ajaxComplete", "ajaxError", "ajaxSuccess", "ajaxSend" ], function( i, type ){
    jQuery.fn[ type ] = function( fn ){
        return this.on( type, fn );
    };
});

jQuery.extend({

    // Counter for holding the number of active queries
    active: 0,

    // Last-Modified header cache for next request
    lastModified: {},
    etag: {},

    //ajax默认参数
    ajaxSettings: {
        url: ajaxLocation,//ajaxLocation = location.href;默认是当前页面地址
        type: "GET",
        isLocal: rlocalProtocol.test( ajaxLocParts[ 1 ] ), //是否本地
        global: true, //是否能触发全局事件参数
        processData: true,
        async: true,
        contentType: "application/x-www-form-urlencoded; charset=UTF-8",//数据编码操作，
        
        //注释是一样的，注释不写就是undefined，
        /*
        timeout: 0,     //超时处理，超时就提示是否继续等待还是离开还是刷新
        data: null,
        dataType: null,
        username: null,    //服务器的验证
        password: null,
        cache: null,   //cache:false,请求后面加一个时间戳，不会有缓存
        throws: false,  //
        traditional: false,  //传统模式
        headers: {},
        */

        accepts: {
            "*": allTypes,
            text: "text/plain",
            html: "text/html",
            xml: "application/xml, text/xml",
            json: "application/json, text/javascript"
        },

        //检测响应头信息，判断返回的类型。
        contents: {
            xml: /xml/,
            html: /html/,
            json: /json/
        },

        responseFields: {
            xml: "responseXML",
            text: "responseText",
            json: "responseJSON"
        },

        // 根据返回的响应头信息，做不同的转换。
        converters: {

            // Convert anything to text
            "* text": String,

            // Text to html (true = no transformation)
            "text html": true,

            // Evaluate text as a json expression
            "text json": jQuery.parseJSON,

            // Parse text as xml
            "text xml": jQuery.parseXML
        },

        // For options that shouldn‘t be deep extended:
        // you can add your own custom options here if
        // and when you create one that shouldn‘t be
        // deep extended (see ajaxExtend)
        flatOptions: {
            url: true,
            context: true
        }
    },

    // 对json继承的封装
    ajaxSetup: function( target, settings ) {
        return settings ?

            //继承json过去
            ajaxExtend( ajaxExtend( target, jQuery.ajaxSettings ), settings ) :

            // Extending ajaxSettings
            ajaxExtend( jQuery.ajaxSettings, target );
    },

    ajaxPrefilter: addToPrefiltersOrTransports( prefilters ),
    ajaxTransport: addToPrefiltersOrTransports( transports ),

    // Main method
    /*
        $.ajax({
            url:url,
            type:‘post‘, 
            success : function(){},
            error:function(){}
        });
        
        $.ajax(‘url‘,{
            type:‘post‘, 
            success : function(){},
            error:function(){}
        });
    */
    ajax: function( url, options ) {//url是地址，options是json
        if ( typeof url === "object" ) {//url是json就赋值给options
            options = url;
            url = undefined;
        }

        // Force options to be an object
        options = options || {};

        var transport,
            // URL without anti-cache param
            cacheURL,
            // Response headers
            responseHeadersString,
            responseHeaders,
            // timeout handle
            timeoutTimer,
            // Cross-domain detection vars
            parts,
            // To know if global events are to be dispatched
            fireGlobals,
            // Loop variable
            i,
            //options覆盖默认参数，继承
            s = jQuery.ajaxSetup( {}, options ),
            // Callbacks context
            callbackContext = s.context || s,
            // Context for global events is callbackContext if it is a DOM node or jQuery collection
            globalEventContext = s.context && ( callbackContext.nodeType || callbackContext.jquery ) ?
                jQuery( callbackContext ) :
                jQuery.event,
            // 延迟对象，回调对象
            deferred = jQuery.Deferred(),
            completeDeferred = jQuery.Callbacks("once memory"),
            // Status-dependent callbacks
            statusCode = s.statusCode || {},
            // Headers (they are sent all at once)
            requestHeaders = {},
            requestHeadersNames = {},
            // The jqXHR state
            state = 0,
            // Default abort message
            strAbort = "canceled",
            // Fake xhr
            jqXHR = {
                readyState: 0,//0--4,4的时候就是完成了

                // 获取响应头
                getResponseHeader: function( key ) {
                    var match;
                    if ( state === 2 ) {
                        if ( !responseHeaders ) {
                            responseHeaders = {};
                            while ( (match = rheaders.exec( responseHeadersString )) ) {
                                responseHeaders[ match[1].toLowerCase() ] = match[ 2 ];
                            }
                        }
                        match = responseHeaders[ key.toLowerCase() ];
                    }
                    return match == null ? null : match;
                },

                // Raw string
                getAllResponseHeaders: function() {
                    return state === 2 ? responseHeadersString : null;
                },

                // 设置请求头
                setRequestHeader: function( name, value ) {
                    var lname = name.toLowerCase();
                    if ( !state ) {
                        name = requestHeadersNames[ lname ] = requestHeadersNames[ lname ] || name;
                        requestHeaders[ name ] = value;
                    }
                    return this;
                },

                // Overrides response content-type header
                overrideMimeType: function( type ) {
                    if ( !state ) {
                        s.mimeType = type;
                    }
                    return this;
                },

                // Status-dependent callbacks
                statusCode: function( map ) {
                    var code;
                    if ( map ) {
                        if ( state < 2 ) {
                            for ( code in map ) {
                                // Lazy-add the new callback in a way that preserves old ones
                                statusCode[ code ] = [ statusCode[ code ], map[ code ] ];
                            }
                        } else {
                            // Execute the appropriate callbacks
                            jqXHR.always( map[ jqXHR.status ] );
                        }
                    }
                    return this;
                },

                // 错误的时候，例如超时，报错
                abort: function( statusText ) {
                    var finalText = statusText || strAbort;
                    if ( transport ) {
                        transport.abort( finalText );
                    }
                    done( 0, finalText );
                    return this;
                }
            };

        // 方法加进去
        deferred.promise( jqXHR ).complete = completeDeferred.add;
        jqXHR.success = jqXHR.done;
        jqXHR.error = jqXHR.fail;

        // 对url处理，
        s.url = ( ( url || s.url || ajaxLocation ) + "" ).replace( rhash, "" )
            .replace( rprotocol, ajaxLocParts[ 1 ] + "//" );

        // Alias method option to type as per ticket #12004
        s.type = options.method || options.type || s.method || s.type;

        // Extract dataTypes list
        s.dataTypes = jQuery.trim( s.dataType || "*" ).toLowerCase().match( core_rnotwhite ) || [""];

        // 跨域处理，不跟本网页是同一个主机地址。
        if ( s.crossDomain == null ) {
            parts = rurl.exec( s.url.toLowerCase() );
            s.crossDomain = !!( parts &&
                ( parts[ 1 ] !== ajaxLocParts[ 1 ] || parts[ 2 ] !== ajaxLocParts[ 2 ] ||
                    ( parts[ 3 ] || ( parts[ 1 ] === "http:" ? "80" : "443" ) ) !==
                        ( ajaxLocParts[ 3 ] || ( ajaxLocParts[ 1 ] === "http:" ? "80" : "443" ) ) )
            );
        }

        // Convert data if not already a string
        if ( s.data && s.processData && typeof s.data !== "string" ) {
            s.data = jQuery.param( s.data, s.traditional );
        }

        // 触发回调
        inspectPrefiltersOrTransports( prefilters, s, options, jqXHR );

        // 请求完成了
        if ( state === 2 ) {
            return jqXHR;
        }

        // We can fire global events as of now if asked to
        fireGlobals = s.global;

        // Watch for a new set of requests
        if ( fireGlobals && jQuery.active++ === 0 ) {
            jQuery.event.trigger("ajaxStart");
        }

        // Uppercase the type
        s.type = s.type.toUpperCase();

        // Determine if request has content
        s.hasContent = !rnoContent.test( s.type );

        // Save the URL in case we‘re toying with the If-Modified-Since
        // and/or If-None-Match header later on
        cacheURL = s.url;

        // More options handling for requests with no content
        if ( !s.hasContent ) {

            // If data is available, append data to url
            if ( s.data ) {
                cacheURL = ( s.url += ( ajax_rquery.test( cacheURL ) ? "&" : "?" ) + s.data );
                // #9682: remove data so that it‘s not used in an eventual retry
                delete s.data;
            }

            // 不缓存就添加随机数
            if ( s.cache === false ) {
                s.url = rts.test( cacheURL ) ?

                    // If there is already a ‘_‘ parameter, set its value
                    cacheURL.replace( rts, "$1_=" + ajax_nonce++ ) :

                    // Otherwise add one to the end
                    cacheURL + ( ajax_rquery.test( cacheURL ) ? "&" : "?" ) + "_=" + ajax_nonce++;
            }
        }

        // 设置头信息，数据没有改变走缓存，通过后端配合，数据改变发起新的请求。
        if ( s.ifModified ) {
            if ( jQuery.lastModified[ cacheURL ] ) {
                jqXHR.setRequestHeader( "If-Modified-Since", jQuery.lastModified[ cacheURL ] );
            }
            if ( jQuery.etag[ cacheURL ] ) {
                jqXHR.setRequestHeader( "If-None-Match", jQuery.etag[ cacheURL ] );
            }
        }

        // Set the correct header, if data is being sent
        if ( s.data && s.hasContent && s.contentType !== false || options.contentType ) {
            jqXHR.setRequestHeader( "Content-Type", s.contentType );
        }

        // 设置请求类型
        jqXHR.setRequestHeader(
            "Accept",
            s.dataTypes[ 0 ] && s.accepts[ s.dataTypes[0] ] ?
                s.accepts[ s.dataTypes[0] ] + ( s.dataTypes[ 0 ] !== "*" ? ", " + allTypes + "; q=0.01" : "" ) :
                s.accepts[ "*" ]
        );

        // Check for headers option
        for ( i in s.headers ) {
            jqXHR.setRequestHeader( i, s.headers[ i ] );
        }

        // Allow custom headers/mimetypes and early abort
        if ( s.beforeSend && ( s.beforeSend.call( callbackContext, jqXHR, s ) === false || state === 2 ) ) {
            // Abort if not done already and return
            return jqXHR.abort();
        }

        // aborting is no longer a cancellation
        strAbort = "abort";

        // Install callbacks on deferreds
        for ( i in { success: 1, error: 1, complete: 1 } ) {
            jqXHR[ i ]( s[ i ] );
        }

        // Get transport
        transport = inspectPrefiltersOrTransports( transports, s, options, jqXHR );

        // If no transport, we auto-abort
        if ( !transport ) {
            done( -1, "No Transport" );
        } else {
            jqXHR.readyState = 1;

            // Send global event
            if ( fireGlobals ) {
                globalEventContext.trigger( "ajaxSend", [ jqXHR, s ] );
            }
            // Timeout
            if ( s.async && s.timeout > 0 ) {
                timeoutTimer = setTimeout(function() {
                    jqXHR.abort("timeout");
                }, s.timeout );
            }

            try {
                state = 1;
                transport.send( requestHeaders, done );
            } catch ( e ) {
                // Propagate exception as error if not done
                if ( state < 2 ) {
                    done( -1, e );
                // Simply rethrow otherwise
                } else {
                    throw e;
                }
            }
        }

        // Callback for when everything is done
        function done( status, nativeStatusText, responses, headers ) {
            var isSuccess, success, error, response, modified,
                statusText = nativeStatusText;

            // Called once
            if ( state === 2 ) {
                return;
            }

            // State is "done" now
            state = 2;

            // Clear timeout if it exists
            if ( timeoutTimer ) {
                clearTimeout( timeoutTimer );
            }

            // Dereference transport for early garbage collection
            // (no matter how long the jqXHR object will be used)
            transport = undefined;

            // Cache response headers
            responseHeadersString = headers || "";

            // Set readyState
            jqXHR.readyState = status > 0 ? 4 : 0;

            // Determine if successful
            isSuccess = status >= 200 && status < 300 || status === 304;

            // Get response data
            if ( responses ) {
                response = ajaxHandleResponses( s, jqXHR, responses );
            }

            // Convert no matter what (that way responseXXX fields are always set)
            response = ajaxConvert( s, response, jqXHR, isSuccess );

            // If successful, handle type chaining
            if ( isSuccess ) {

                // Set the If-Modified-Since and/or If-None-Match header, if in ifModified mode.
                if ( s.ifModified ) {
                    modified = jqXHR.getResponseHeader("Last-Modified");
                    if ( modified ) {
                        jQuery.lastModified[ cacheURL ] = modified;
                    }
                    modified = jqXHR.getResponseHeader("etag");
                    if ( modified ) {
                        jQuery.etag[ cacheURL ] = modified;
                    }
                }

                // if no content
                if ( status === 204 || s.type === "HEAD" ) {
                    statusText = "nocontent";

                // if not modified
                } else if ( status === 304 ) {
                    statusText = "notmodified";

                // If we have data, let‘s convert it
                } else {
                    statusText = response.state;
                    success = response.data;
                    error = response.error;
                    isSuccess = !error;
                }
            } else {
                // We extract error from statusText
                // then normalize statusText and status for non-aborts
                error = statusText;
                if ( status || !statusText ) {
                    statusText = "error";
                    if ( status < 0 ) {
                        status = 0;
                    }
                }
            }

            // Set data for the fake xhr object
            jqXHR.status = status;
            jqXHR.statusText = ( nativeStatusText || statusText ) + "";

            // Success/Error
            if ( isSuccess ) {
                deferred.resolveWith( callbackContext, [ success, statusText, jqXHR ] );
            } else {
                deferred.rejectWith( callbackContext, [ jqXHR, statusText, error ] );
            }

            // Status-dependent callbacks
            jqXHR.statusCode( statusCode );
            statusCode = undefined;

            if ( fireGlobals ) {
                globalEventContext.trigger( isSuccess ? "ajaxSuccess" : "ajaxError",
                    [ jqXHR, s, isSuccess ? success : error ] );
            }

            // Complete
            completeDeferred.fireWith( callbackContext, [ jqXHR, statusText ] );

            if ( fireGlobals ) {
                globalEventContext.trigger( "ajaxComplete", [ jqXHR, s ] );
                // Handle the global AJAX counter
                if ( !( --jQuery.active ) ) {
                    jQuery.event.trigger("ajaxStop");
                }
            }
        }
//ajax方法结束后，返回jqXHR对象，$.ajax()方法后面就可以调用done、fail方法，$.ajax({url:url}).done().fail();
        return jqXHR;
    },

    getJSON: function( url, data, callback ) {
        return jQuery.get( url, data, callback, "json" );//调用jQuery.ajax()
    },

    getScript: function( url, callback ) {//请求js不传递参数
        return jQuery.get( url, undefined, callback, "script" );
        //调用jQuery.ajax()
    }
});

//["get","post"]每一个元素调用function( i, method )，i是索引method是‘get‘、‘post‘
jQuery.each( [ "get", "post" ], function( i, method ) {
//get，post挂载到jQuery静态方法,通过中括号挂载。
//$.get(‘url‘,{‘aa‘:123},function(){‘成功回调‘},‘返回数据类型xml、json‘)
    jQuery[ method ] = function( url, data, callback, type ) {
        // shift arguments if data argument was omitted
        if ( jQuery.isFunction( data ) ) {
            type = type || callback;
            callback = data;
            data = undefined;
        }

        return jQuery.ajax({
            url: url,
            type: method,
            dataType: type,
            data: data,
            success: callback
        });
    };
});

/* Handles responses to an ajax request:
 * - finds the right dataType (mediates between content-type and expected dataType)
 * - returns the corresponding response
 */
function ajaxHandleResponses( s, jqXHR, responses ) {

    var ct, type, finalDataType, firstDataType,
        contents = s.contents,
        dataTypes = s.dataTypes;

    // Remove auto dataType and get content-type in the process
    while( dataTypes[ 0 ] === "*" ) {
        dataTypes.shift();
        if ( ct === undefined ) {
            ct = s.mimeType || jqXHR.getResponseHeader("Content-Type");
        }
    }

    // Check if we‘re dealing with a known content-type
    if ( ct ) {
        for ( type in contents ) {
            if ( contents[ type ] && contents[ type ].test( ct ) ) {
                dataTypes.unshift( type );
                break;
            }
        }
    }

    // Check to see if we have a response for the expected dataType
    if ( dataTypes[ 0 ] in responses ) {
        finalDataType = dataTypes[ 0 ];
    } else {
        // Try convertible dataTypes
        for ( type in responses ) {
            if ( !dataTypes[ 0 ] || s.converters[ type + " " + dataTypes[0] ] ) {
                finalDataType = type;
                break;
            }
            if ( !firstDataType ) {
                firstDataType = type;
            }
        }
        // Or just use first one
        finalDataType = finalDataType || firstDataType;
    }

    // If we found a dataType
    // We add the dataType to the list if needed
    // and return the corresponding response
    if ( finalDataType ) {
        if ( finalDataType !== dataTypes[ 0 ] ) {
            dataTypes.unshift( finalDataType );
        }
        return responses[ finalDataType ];
    }
}

//类型转换器，匹配返回的数据类型
function ajaxConvert( s, response, jqXHR, isSuccess ) {
    var conv2, current, conv, tmp, prev,
        converters = {},
        // Work with a copy of dataTypes in case we need to modify it for conversion
        dataTypes = s.dataTypes.slice();

    // Create converters map with lowercased keys
    if ( dataTypes[ 1 ] ) {
        for ( conv in s.converters ) {
            converters[ conv.toLowerCase() ] = s.converters[ conv ];
        }
    }

    current = dataTypes.shift();

    // Convert to each sequential dataType
    while ( current ) {

        if ( s.responseFields[ current ] ) {
            jqXHR[ s.responseFields[ current ] ] = response;
        }

        // Apply the dataFilter if provided
        if ( !prev && isSuccess && s.dataFilter ) {
            response = s.dataFilter( response, s.dataType );
        }

        prev = current;
        current = dataTypes.shift();

        if ( current ) {

        // There‘s only work to do if current dataType is non-auto
            if ( current === "*" ) {

                current = prev;

            // Convert response if prev dataType is non-auto and differs from current
            } else if ( prev !== "*" && prev !== current ) {

                // Seek a direct converter
                conv = converters[ prev + " " + current ] || converters[ "* " + current ];

                // If none found, seek a pair
                if ( !conv ) {
                    for ( conv2 in converters ) {

                        // If conv2 outputs current
                        tmp = conv2.split( " " );
                        if ( tmp[ 1 ] === current ) {

                            // If prev can be converted to accepted input
                            conv = converters[ prev + " " + tmp[ 0 ] ] ||
                                converters[ "* " + tmp[ 0 ] ];
                            if ( conv ) {
                                // Condense equivalence converters
                                if ( conv === true ) {
                                    conv = converters[ conv2 ];

                                // Otherwise, insert the intermediate dataType
                                } else if ( converters[ conv2 ] !== true ) {
                                    current = tmp[ 0 ];
                                    dataTypes.unshift( tmp[ 1 ] );
                                }
                                break;
                            }
                        }
                    }
                }

                // Apply converter (if not an equivalence)
                if ( conv !== true ) {

                    // Unless errors are allowed to bubble, catch and return them
                    if ( conv && s[ "throws" ] ) {
                        response = conv( response );
                    } else {
                        try {
                            response = conv( response );
                        } catch ( e ) {
                            return { state: "parsererror", error: conv ? e : "No conversion from " + prev + " to " + current };
                        }
                    }
                }
            }
        }
    }

    return { state: "success", data: response };
}
// Install script dataType
jQuery.ajaxSetup({
    accepts: {
        script: "text/javascript, application/javascript, application/ecmascript, application/x-ecmascript"
    },
    contents: {
        script: /(?:java|ecma)script/
    },
    converters: {
        "text script": function( text ) {
            jQuery.globalEval( text );
            return text;
        }
    }
});

// 发送ajax之前对数据做处理
jQuery.ajaxPrefilter( "script", function( s ) {
    if ( s.cache === undefined ) {
        s.cache = false;
    }
    if ( s.crossDomain ) {
        s.type = "GET";
    }
});

// Bind script tag hack transport
jQuery.ajaxTransport( "script", function( s ) {
    // This transport only deals with cross domain requests
    if ( s.crossDomain ) {
        var script, callback;
        return {
            send: function( _, complete ) {
                script = jQuery("<script>").prop({
                    async: true,
                    charset: s.scriptCharset,
                    src: s.url
                }).on(
                    "load error",
                    callback = function( evt ) {
                        script.remove();
                        callback = null;
                        if ( evt ) {
                            complete( evt.type === "error" ? 404 : 200, evt.type );
                        }
                    }
                );
                document.head.appendChild( script[ 0 ] );
            },
            abort: function() {
                if ( callback ) {
                    callback();
                }
            }
        };
    }
});
var oldCallbacks = [],
    rjsonp = /(=)\?(?=&|$)|\?\?/;

// Default jsonp settings
jQuery.ajaxSetup({
    jsonp: "callback",
    jsonpCallback: function() {
        var callback = oldCallbacks.pop() || ( jQuery.expando + "_" + ( ajax_nonce++ ) );
        this[ callback ] = true;
        return callback;
    }
});

// Detect, normalize options and install callbacks for jsonp requests
jQuery.ajaxPrefilter( "json jsonp", function( s, originalSettings, jqXHR ) {

    var callbackName, overwritten, responseContainer,
        jsonProp = s.jsonp !== false && ( rjsonp.test( s.url ) ?
            "url" :
            typeof s.data =http://www.mamicode.com/=="string" && !( s.contentType || "" ).indexOf("application/x-www-form-urlencoded") && rjsonp.test( s.data ) && "data"
        );

    // Handle iff the expected data type is "jsonp" or we have a parameter to set
    if ( jsonProp || s.dataTypes[ 0 ] === "jsonp" ) {

        // Get callback name, remembering preexisting value associated with it
        callbackName = s.jsonpCallback = jQuery.isFunction( s.jsonpCallback ) ?
            s.jsonpCallback() :
            s.jsonpCallback;

        // Insert callback into url or form data
        if ( jsonProp ) {
            s[ jsonProp ] = s[ jsonProp ].replace( rjsonp, "$1" + callbackName );
        } else if ( s.jsonp !== false ) {
            s.url += ( ajax_rquery.test( s.url ) ? "&" : "?" ) + s.jsonp + "=" + callbackName;
        }

        // Use data converter to retrieve json after script execution
        s.converters["script json"] = function() {
            if ( !responseContainer ) {
                jQuery.error( callbackName + " was not called" );
            }
            return responseContainer[ 0 ];
        };

        // force json dataType
        s.dataTypes[ 0 ] = "json";

        // Install callback
        overwritten = window[ callbackName ];
        window[ callbackName ] = function() {
            responseContainer = arguments;
        };

        // Clean-up function (fires after converters)
        jqXHR.always(function() {
            // Restore preexisting value
            window[ callbackName ] = overwritten;

            // Save back as free
            if ( s[ callbackName ] ) {
                // make sure that re-using the options doesn‘t screw things around
                s.jsonpCallback = originalSettings.jsonpCallback;

                // save the callback name for future use
                oldCallbacks.push( callbackName );
            }

            // Call if it was a function and we have a response
            if ( responseContainer && jQuery.isFunction( overwritten ) ) {
                overwritten( responseContainer[ 0 ] );
            }

            responseContainer = overwritten = undefined;
        });

        // Delegate to script
        return "script";
    }
});
jQuery.ajaxSettings.xhr = function() {
    try {
        return new XMLHttpRequest();
    } catch( e ) {}
};

var xhrSupported = jQuery.ajaxSettings.xhr(),
    xhrSuccessStatus = {
        // file protocol always yields status code 0, assume 200
        0: 200,
        // Support: IE9
        // #1450: sometimes IE returns 1223 when it should be 204
        1223: 204
    },
    // Support: IE9
    // We need to keep track of outbound xhr and abort them manually
    // because IE is not smart enough to do it all by itself
    xhrId = 0,
    xhrCallbacks = {};

if ( window.ActiveXObject ) {
    jQuery( window ).on( "unload", function() {
        for( var key in xhrCallbacks ) {
            xhrCallbacks[ key ]();
        }
        xhrCallbacks = undefined;
    });
}

jQuery.support.cors = !!xhrSupported && ( "withCredentials" in xhrSupported );
jQuery.support.ajax = xhrSupported = !!xhrSupported;

jQuery.ajaxTransport(function( options ) {
    var callback;
    // Cross domain only allowed if supported through XMLHttpRequest
    if ( jQuery.support.cors || xhrSupported && !options.crossDomain ) {
        return {
            send: function( headers, complete ) {
                var i, id,
                //xhr是原生XMLHttpRequest对象
                    xhr = options.xhr();
                xhr.open( options.type, options.url, options.async, options.username, options.password );
                // Apply custom fields if provided
                if ( options.xhrFields ) {
                    for ( i in options.xhrFields ) {
                        xhr[ i ] = options.xhrFields[ i ];
                    }
                }
                // 跨域处理
                if ( options.mimeType && xhr.overrideMimeType ) {
                    xhr.overrideMimeType( options.mimeType );
                }
                // X-Requested-With header
                // For cross-domain requests, seeing as conditions for a preflight are
                // akin to a jigsaw puzzle, we simply never set it to be sure.
                // (it can always be set on a per-request basis or even using ajaxSetup)
                // For same-domain requests, won‘t change header if already provided.
                if ( !options.crossDomain && !headers["X-Requested-With"] ) {
                    headers["X-Requested-With"] = "XMLHttpRequest";
                }
                // Set headers
                for ( i in headers ) {
                    xhr.setRequestHeader( i, headers[ i ] );
                }
                // Callback
                callback = function( type ) {
                    return function() {
                        if ( callback ) {
                            delete xhrCallbacks[ id ];
                            callback = xhr.onload = xhr.onerror = null;
                            if ( type === "abort" ) {
                                xhr.abort();
                            } else if ( type === "error" ) {
                                complete(
                                    // file protocol always yields status 0, assume 404
                                    xhr.status || 404,
                                    xhr.statusText
                                );
                            } else {
                                complete(
                                    xhrSuccessStatus[ xhr.status ] || xhr.status,
                                    xhr.statusText,
                                    // Support: IE9
                                    // #11426: When requesting binary data, IE9 will throw an exception
                                    // on any attempt to access responseText
                                    typeof xhr.responseText === "string" ? {
                                        text: xhr.responseText
                                    } : undefined,
                                    xhr.getAllResponseHeaders()
                                );
                            }
                        }
                    };
                };
                // 真正完成才会走onload
                xhr.onload = callback();
                xhr.onerror = callback("error");
                // Create the abort callback
                callback = xhrCallbacks[( id = xhrId++ )] = callback("abort");
                // Do send the request
                // This may raise an exception which is actually
                // handled in jQuery.ajax (so no try/catch here)
                //发送
                xhr.send( options.hasContent && options.data || null );
            },
            abort: function() {
                if ( callback ) {
                    callback();
                }
            }
        };
    }
});

}