Read the onBlur API Reference, whatever you put it on it will create an event handler on it, so if you simply put it on the repeater, then the whole repeater will be an event handler.
https://www.wix.com/corvid/reference/$w.FocusMixin.html#onBlur
If you want to do certain parts of the repeater then simply follow what it tells you on the reference.
…To get a scoped selector for working with elements in repeater items, use the $w.at() function and pass it the context property of the event parameter: $item = $w.at(event.context). To learn more, see here .