jquery1.5+ ajax跨域请求在IE下没反应分析

  jquery1.5+重写过ajax代码,增加了跨域判断(自动判断ajax请求的url地址是否和当前访问的页面同源,jquery1.4-版本没有增加跨域判断,所以直接发送ajax请求,这样就和浏览器的安全设置有关了),jquery1.5+如果跨域访问并且不支持跨域请求(这些都是jquery代码自动判断的),就不会发送ajax请求(所以浏览器安全设置被忽略),导致没有触发任何事件,所以jquery1.4+能在ie配置安全区域的通过域访问数据源后可以跨域请求,而jquery1.5+就完全没有反应。

  具体可以参考http://code.jquery.com/jquery-1.10.2.js未压缩的源代码中的这些代码,是否支持跨域jquery是通过xhr的withCredentials属性来判断,在IE10-之前的版本都没有实现,所以jquery1.5+版本在ie下都默认xhr对象不支持跨域(不在考虑ie浏览器的安全配置)。
 

// Functions to create xhrs
function createStandardXHR() {
    try {
        return new window.XMLHttpRequest();
    } catch( e ) {}
}
function createActiveXHR() {
    try {
        return new window.ActiveXObject("Microsoft.XMLHTTP");
    } catch( e ) {}
}
// Create the request object
// (This is still attached to ajaxSettings for backward compatibility)
jQuery.ajaxSettings.xhr = window.ActiveXObject ?
    /* Microsoft failed to properly
     * implement the XMLHttpRequest in IE7 (can't request local files),
     * so we use the ActiveXObject when it is available
     * Additionally XMLHttpRequest can be disabled in IE7/IE8 so
     * we need a fallback.
     */
    function() {
        return !this.isLocal && createStandardXHR() || createActiveXHR();
    } :
    // For all other browsers, use the standard XMLHttpRequest object
    createStandardXHR;
// Determine support properties
xhrSupported = jQuery.ajaxSettings.xhr();
jQuery.support.cors = !!xhrSupported && ( "withCredentials" in xhrSupported );
xhrSupported = jQuery.support.ajax = !!xhrSupported;
// Create transport if the browser can provide an xhr
if ( xhrSupported ) {
    jQuery.ajaxTransport(function( s ) {
        // Cross domain only allowed if supported through XMLHttpRequest
        if ( !s.crossDomain || jQuery.support.cors ) {
            var callback;
            return {
                send: function( headers, complete ) {
                    // Get a new xhr
                    var handle, i,
                        xhr = s.xhr();
                    // Open the socket
                    // Passing null username, generates a login popup on Opera (#2865)
                    if ( s.username ) {
                        xhr.open( s.type, s.url, s.async, s.username, s.password );
                    } else {
                        xhr.open( s.type, s.url, s.async );
                    }
                    // Apply custom fields if provided
                    if ( s.xhrFields ) {
                        for ( i in s.xhrFields ) {
                            xhr[ i ] = s.xhrFields[ i ];
                        }
                    }
                    // Override mime type if needed
                    if ( s.mimeType && xhr.overrideMimeType ) {
                        xhr.overrideMimeType( s.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 ( !s.crossDomain && !headers["X-Requested-With"] ) {
                        headers["X-Requested-With"] = "XMLHttpRequest";
                    }
                    // Need an extra try/catch for cross domain requests in Firefox 3
                    try {
                        for ( i in headers ) {
                            xhr.setRequestHeader( i, headers[ i ] );
                        }
                    } catch( err ) {}
                    // Do send the request
                    // This may raise an exception which is actually
                    // handled in jQuery.ajax (so no try/catch here)
                    xhr.send( ( s.hasContent && s.data ) || null );
                    // Listener
                    callback = function( _, isAbort ) {
                        var status, responseHeaders, statusText, responses;
                        // Firefox throws exceptions when accessing properties
                        // of an xhr when a network error occurred
                        // http://helpful.knobs-dials.com/index.php/Component_returned_failure_code:_0x80040111_(NS_ERROR_NOT_AVAILABLE)
                        try {
                            // Was never called and is aborted or complete
                            if ( callback && ( isAbort || xhr.readyState === 4 ) ) {
                                // Only called once
                                callback = undefined;
                                // Do not keep as active anymore
                                if ( handle ) {
                                    xhr.onreadystatechange = jQuery.noop;
                                    if ( xhrOnUnloadAbort ) {
                                        delete xhrCallbacks[ handle ];
                                    }
                                }
                                // If it's an abort
                                if ( isAbort ) {
                                    // Abort it manually if needed
                                    if ( xhr.readyState !== 4 ) {
                                        xhr.abort();
                                    }
                                } else {
                                    responses = {};
                                    status = xhr.status;
                                    responseHeaders = xhr.getAllResponseHeaders();
                                    // When requesting binary data, IE6-9 will throw an exception
                                    // on any attempt to access responseText (#11426)
                                    if ( typeof xhr.responseText === "string" ) {
                                        responses.text = xhr.responseText;
                                    }
                                    // Firefox throws an exception when accessing
                                    // statusText for faulty cross-domain requests
                                    try {
                                        statusText = xhr.statusText;
                                    } catch( e ) {
                                        // We normalize with Webkit giving an empty statusText
                                        statusText = "";
                                    }
                                    // Filter status for non standard behaviors
                                    // If the request is local and we have data: assume a success
                                    // (success with no data won't get notified, that's the best we
                                    // can do given current implementations)
                                    if ( !status && s.isLocal && !s.crossDomain ) {
                                        status = responses.text ? 200 : 404;
                                    // IE - #1450: sometimes returns 1223 when it should be 204
                                    } else if ( status === 1223 ) {
                                        status = 204;
                                    }
                                }
                            }
                        } catch( firefoxAccessException ) {
                            if ( !isAbort ) {
                                complete( -1, firefoxAccessException );
                            }
                        }
                        // Call complete if needed
                        if ( responses ) {
                            complete( status, statusText, responses, responseHeaders );
                        }
                    };
                    if ( !s.async ) {
                        // if we're in sync mode we fire the callback
                        callback();
                    } else if ( xhr.readyState === 4 ) {
                        // (IE6 & IE7) if it's in cache and has been
                        // retrieved directly we need to fire the callback
                        setTimeout( callback );
                    } else {
                        handle = ++xhrId;
                        if ( xhrOnUnloadAbort ) {
                            // Create the active xhrs callbacks list if needed
                            // and attach the unload handler
                            if ( !xhrCallbacks ) {
                                xhrCallbacks = {};
                                jQuery( window ).unload( xhrOnUnloadAbort );
                            }
                            // Add to list of active xhrs callbacks
                            xhrCallbacks[ handle ] = callback;
                        }
                        xhr.onreadystatechange = callback;
                    }
                },
                abort: function() {
                    if ( callback ) {
                        callback( undefined, true );
                    }
                }
            };
        }
    });
}

 

 

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