Enable the auto-complete result in User and Issue Picker fields in plugin

I am developing a jira server plugin. The plugin has built - in the user picker and the issue picker field, like the picture bellow:
The popups for issue and user selection works properly but the autocompletion doesn’t work. Does anyone has an idea how can I enable the autocomplete functionality?
Here is some part of the code:

<a class="popup-trigger" href="#" autocomplete="on"