Needed this today and stumbled on this post.
I’m dynamically changing things via select2_ajax_data
based on other field values, so I needed the value of a different field in a repeater row.
This is the idea. Works well enough.
// $input is coming from select2_ajax_data filter,
// so it's the current field input.
var fields = acf.getFields(
{
key: 'my_field_key',
parent: $input.parents( '.acf-row' ),
}
);
if ( fields ) {
var value = fields.shift().val();
}