In order to add a custom targeting filter, which would be a way to determine who sees your ethnio screener according to data in your system, you would have to send a variable to our JS. That way if you track something about your site visitors or customers, you can use that data to decide who sees a screener.
For example, let's say you track which customers have purchased an orange or an apple. If you pass the variable to ethnio code, you can then only show your screener to people that have bought an orange.
So your back-end would be setup with this syntax to basically tell ethnio whether or not to display a screener based on something internal you track about your customers or site visitors. The condition would be if our JS receives the ethn.io/37137?fruit_purchases=apples and that way every single page load where you send a suffix to the URL we can decide whether or not to display the ethnio screener on that page load based on any filter you setup. And you can have as many as you'd like by separating them with &.
Excluding: The Null State
If you want to target certain types of data, but exclude all others, you just need to add an "other" variable and parameter. That way you can make sure a single targeting filter will be using the "some" state, but you can call it anything you'd like and make sure it's deselected or greyed out: