同步 XMLHttpRequest 弃用警告解决方案的可行性

Question

This problem has been reported on many forums, including this one, and I've found a solution that is apparently unique, although I'm not sure if it's wise. It certainly does work, but it's probably something someone closer to the JQuery development or one of its members might be able to answer with authority.

The issue that many others and I have experienced is a console error message with this text:

Synchronous XMLHttpRequest on the main thread is deprecated because of its detrimental effects to the end user's experience. For more help, check http://xhr.spec.whatwg.org/

In my case, and in the cases of many others, it references the jquery.js file, specifically this line

xhr.open( options.type, options.url, options.async; options.username, options.password );

The relevant information at http://xhr.spec.whatwg.org/ states:

Developers must not pass false for the async argument when the JavaScript global environment is a document environment.

I have many complex, minified routines written by others that make use of JQuery, and I'm no expert at finding where in those routines the error would be created.

It then hit me to simply substitute true for options.async in the jquery.js file, like this:

xhr.open( options.type, options.url, true, options.username, options.password );

Voila! The problem vanished on every browser where the console reported an error. (Locating and editing the correlative code in the minified JQuery.min.js file was a snap; finding it in all of the other routines that depend on JQuery would have been tedious if not mildly impossible.)

But my question is this: Is this apparent hack of a solution unwise? My site does work, and none of the routines that make use of JQuery has a problem with this. Commentary much appreciated.

Answer 1

THE PROBLEM IS IN THE JQUERY DISTRIBUTABLE ITSELF

The cause of the problem is in the jquery.js file as found in the current version 2.1.4. Despite documenting options.async as a deprecated parameter that should only be passed a value of true , the jquery.js file itself calls the xhr.open file using data defined earlier in the file with the parameter set to false . This is the offending routine in the jquery.js file:

jQuery._evalUrl = function( url ) {
    return jQuery.ajax({
        url: url,
        type: "GET",
        dataType: "script",
        async: false,
        global: false,
        "throws": true
    });
};

When async is set to true , the problem vanishes, and the hack solution I had previously used is no longer needed.

Now, seriously, this is something a true JQuery expert should comment on. Why would the JQuery initialization file violate the very standard of usage that it advises its users to follow?