Problems Encountered When Using jQuery.ajax to Upload a Form with Files

When I was helping someone review code today, I encountered a small problem. There are some issues when using jQuery to upload a form with files.

Firstly, because FormData is used, processData: false must be configured in the parameters passed to $.ajax.

Otherwise, an 'Illegal invocation' exception will be thrown because jQuery defaults to processing the data in the data field passed in.

The official document explains it like this:

Secondly, pay attention to the request's Content-Type header, the default is application/x-www-form-urlencoded; charset=UTF-8, which is the format we usually see as 'a=A&b=B'. However, it doesn't work when using FormData.

Add a contentType field to the parameters and set its value to false. If the jQuery version is less than 1.6, then manually set it to multipart/form-data. For specific instructions, please refer to the document description:

I usually used the native XMLHttpRequest before, so I didn't encounter this kind of problem. Since I have encountered it, I must solve it. Therefore, I record it here for future reference.

The above-mentioned issues are introduced by the editor for everyone's use of jQuery.ajax to upload a form with files. I hope it will be helpful to everyone. If you have any questions, please leave a message, and the editor will reply to everyone in time. I would also like to express my sincere gratitude to everyone for their support of the Yell Tutorial website!

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