About the No Transport Error Solution Process for ajax requests in jquery in ie, jqueryajax

Source: Internet
Author: User

About the No Transport Error Solution Process for ajax requests in jquery in ie, jqueryajax

The first background is that the tester found that our webpage was incorrectly displayed in ie9. Actually, all asynchronous interfaces were not executed. Then I started the difficult troubleshooting process. All of our asynchronous interfaces are developed using jQuery's ajax method. The jquery version is 1.11.0.

I first found that the ajax method returned status = 0, statusText = No Transport. Then I started my journey of searching for problems. All the information I found on the Internet said this was caused by cross-origin.$.support.cros=trueYou can. However, the actual interface accessed by our project does not belong to cross-origin. Therefore, although this attribute can solve the problem, the root cause is not found.

So I started to look at jquery's source code, first located the code segment with an error, and first pasted the error point:

 1 // Get transport 2         transport = inspectPrefiltersOrTransports( transports, s, options, jqXHR ); 3  4         // If no transport, we auto-abort 5         if ( !transport ) { 6             done( -1, "No Transport" ); 7         } else { 8             jqXHR.readyState = 1; 9 10             // Send global event11             if ( fireGlobals ) {12                 globalEventContext.trigger( "ajaxSend", [ jqXHR, s ] );13             }14             // Timeout15             if ( s.async && s.timeout > 0 ) {16                 timeoutTimer = setTimeout(function() {17                     jqXHR.abort("timeout");18                 }, s.timeout );19             }20 21             try {22                 state = 1;23                 transport.send( requestHeaders, done );24             } catch ( e ) {25                 // Propagate exception as error if not done26                 if ( state < 2 ) {27                     done( -1, e );28                 // Simply rethrow otherwise29                 } else {30                     throw e;31                 }32             }33         }

 

Transport = false. At the beginning, I couldn't fully understand the jquery source code. So I consulted a great God in our company. Under the guidance of a great god, I started to check why transport = false. After the omnipotent breakpoint debugging, it is found thatoptions.crossDomain = trueThe key code that cannot enter this segment to correctly send the request (the specific code is not used for analysis ). At this point, I finally located the culprit, which was initially added to allow direct access to the api server on the html page.crossDomain=true(Because the html and api server belong to different domain names ). (This is not over yet. Please proceed)

  1 // Determine support properties  2 support.cors = !!xhrSupported && ( "withCredentials" in xhrSupported );  3 xhrSupported = support.ajax = !!xhrSupported;  4   5 // Create transport if the browser can provide an xhr  6 if ( xhrSupported ) {  7   8     jQuery.ajaxTransport(function( options ) {  9         // Cross domain only allowed if supported through XMLHttpRequest 10         if ( !options.crossDomain || support.cors ) { 11  12             var callback; 13  14             return { 15                 send: function( headers, complete ) { 16                     var i, 17                         xhr = options.xhr(), 18                         id = ++xhrId; 19  20                     // Open the socket 21                     xhr.open( options.type, options.url, options.async, options.username, options.password ); 22  23                     // Apply custom fields if provided 24                     if ( options.xhrFields ) { 25                         for ( i in options.xhrFields ) { 26                             xhr[ i ] = options.xhrFields[ i ]; 27                         } 28                     } 29  30                     // Override mime type if needed 31                     if ( options.mimeType && xhr.overrideMimeType ) { 32                         xhr.overrideMimeType( options.mimeType ); 33                     } 34  35                     // X-Requested-With header 36                     // For cross-domain requests, seeing as conditions for a preflight are 37                     // akin to a jigsaw puzzle, we simply never set it to be sure. 38                     // (it can always be set on a per-request basis or even using ajaxSetup) 39                     // For same-domain requests, won't change header if already provided. 40                     if ( !options.crossDomain && !headers["X-Requested-With"] ) { 41                         headers["X-Requested-With"] = "XMLHttpRequest"; 42                     } 43  44                     // Set headers 45                     for ( i in headers ) { 46                         // Support: IE<9 47                         // IE's ActiveXObject throws a 'Type Mismatch' exception when setting 48                         // request header to a null-value. 49                         // 50                         // To keep consistent with other XHR implementations, cast the value 51                         // to string and ignore `undefined`. 52                         if ( headers[ i ] !== undefined ) { 53                             xhr.setRequestHeader( i, headers[ i ] + "" ); 54                         } 55                     } 56  57                     // Do send the request 58                     // This may raise an exception which is actually 59                     // handled in jQuery.ajax (so no try/catch here) 60                     xhr.send( ( options.hasContent && options.data ) || null ); 61  62                     // Listener 63                     callback = function( _, isAbort ) { 64                         var status, statusText, responses; 65  66                         // Was never called and is aborted or complete 67                         if ( callback && ( isAbort || xhr.readyState === 4 ) ) { 68                             // Clean up 69                             delete xhrCallbacks[ id ]; 70                             callback = undefined; 71                             xhr.onreadystatechange = jQuery.noop; 72  73                             // Abort manually if needed 74                             if ( isAbort ) { 75                                 if ( xhr.readyState !== 4 ) { 76                                     xhr.abort(); 77                                 } 78                             } else { 79                                 responses = {}; 80                                 status = xhr.status; 81  82                                 // Support: IE<10 83                                 // Accessing binary-data responseText throws an exception 84                                 // (#11426) 85                                 if ( typeof xhr.responseText === "string" ) { 86                                     responses.text = xhr.responseText; 87                                 } 88  89                                 // Firefox throws an exception when accessing 90                                 // statusText for faulty cross-domain requests 91                                 try { 92                                     statusText = xhr.statusText; 93                                 } catch( e ) { 94                                     // We normalize with Webkit giving an empty statusText 95                                     statusText = ""; 96                                 } 97  98                                 // Filter status for non standard behaviors 99 100                                 // If the request is local and we have data: assume a success101                                 // (success with no data won't get notified, that's the best we102                                 // can do given current implementations)103                                 if ( !status && options.isLocal && !options.crossDomain ) {104                                     status = responses.text ? 200 : 404;105                                 // IE - #1450: sometimes returns 1223 when it should be 204106                                 } else if ( status === 1223 ) {107                                     status = 204;108                                 }109                             }110                         }111 112                         // Call complete if needed113                         if ( responses ) {114                             complete( status, statusText, responses, xhr.getAllResponseHeaders() );115                         }116                     };117 118                     if ( !options.async ) {119                         // if we're in sync mode we fire the callback120                         callback();121                     } else if ( xhr.readyState === 4 ) {122                         // (IE6 & IE7) if it's in cache and has been123                         // retrieved directly we need to fire the callback124                         setTimeout( callback );125                     } else {126                         // Add to the list of active xhr callbacks127                         xhr.onreadystatechange = xhrCallbacks[ id ] = callback;128                     }129                 },130 131                 abort: function() {132                     if ( callback ) {133                         callback( undefined, true );134                     }135                 }136             };137         }138     });139 }

 

It should have ended, but it does not. Although I have addedcrossDomain=trueBut why other browsers can access normally, but ie9 does not. I continue to debug the code, and finally found that the above Code in other browserssupport.cors = trueIn ie9, this attribute is equal to false. From the code above, we can also see that the judgment of this attribute comes fromsupport.cors = !!xhrSupported && ( "withCredentials" in xhrSupported ), WherexhrSupported= new window.XMLHttpRequest()In ie9, XMLHttpRequest does not have the withCredentials attribute. That is to say, this problem is caused by the incompatibility of various browsers due to my misuse of attributes.

Related Article

E-Commerce Solutions

Leverage the same tools powering the Alibaba Ecosystem

Learn more >

Apsara Conference 2019

The Rise of Data Intelligence, September 25th - 27th, Hangzhou, China

Learn more >

Alibaba Cloud Free Trial

Learn and experience the power of Alibaba Cloud with a free trial worth $300-1200 USD

Learn more >

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.