Description

It appears that if I trigger ablur event, immediately after analert() inside a click event handler, it results in an error:

Uncaught TypeError: saved.slice is not a function

This is happening in jQuery 3.7.1 and 4.0.0-beta. But not in 3.5.1. I wonderif this issue might be related.

Link to test case

The way to reproduce this is quite simple:

$('button').on('click',function(e){alert('Hello');$(this).trigger('blur');})

https://jsbin.com/vuquzepidi/edit?html%2Cjs%2Coutput=

I've found that if I useconsole.log instead ofalert() it works just fine. Also if I put the trigger into asetTimeout it works just fine. Likewise if I change it to trigger afocus event it works. I did try afocus before theblur, wondering if the alert might cause the button to loose focus, but no change, and even if it did, I would have expected an error.

Apologies, I haven't yet dug into the code to see what might be happening - I can see in the debugger thatsaved istrue, but I've not looked to see why that is yet.