Is it recommended to use JavaScript in description for a custom field to add the functionality so that a CF will be displayed based on value selected in another CF?

[Nic Brough -Adaptavist- · Accepted solution]

No, it's never recommended to use javascript in description fields.  There are several places you'd need to implement it (more if you have add-ons) and it's quite easy to break even if you caught every place.  Atlassian have also been gradually removing the ability for javascript to be injected into fields.