jQuery - Append a Value to a INPUT, keeping it a Comma Delimited list

Question

I have an input like follows:

I\'d like to be able to append a value to th

Answer 1

$('#attachment-uuids').val(function(i,val) { 
     return val + (!val ? '' : ', ') + '66666';
});

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EDIT: As @mkoryak noted, I'm doing an unnecessary negation of val in the conditional operator. It could be rewritten without the ! as:

(val ? ', ' : '')