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I use Ajax extensively in my JavaScript code. Today I added an Ajax call to a page and nothing happens. The Firefox web console shows a result of "undefined". The exact log entry is:

[11:15:50.733] POST http://mastersw.com/theme/test9.php [undefined 78ms]

(I had to modify the URL to satisfy the editor rules here.)

When I click on the log entry, I see a message dialog with no response. Everything else is correct in the message.

I have checked the Apache logs and there is no sign that the post request got to the server. I use my own JavaScript library Ajax routines. They work everywhere else. I have double checked that the script (test9.php) exists.

I cannot find any documentation on what Firefox means when they say "undefined". Google search returns millions of hits about other things.

The problem seems to be that Firefox is for some reason not completing the post operation and I cannot figure out why.

Update: The JavaScript function invoking the Ajax call was itself being invoked from the onclick handler of an anchor. When I changed the element to a div it worked.

I don't have any idea why Firefox gave an 'undefined' for the post. Chrome complained about an invalid header "Content-Length". Changing to a div fixed this as well.

Peter Mortensen
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user2073777
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  • More generally for the Firefox web console and "undefined": *[Chrome/Firefox console.log always appends a line saying 'undefined'](https://stackoverflow.com/questions/14633968)* – Peter Mortensen Oct 20 '20 at 17:46

1 Answers1

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You need to cancel the click event

$("a").on("click", function (evt) {
    evt.preventDefault();
    //ajax call here
});
epascarello
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