How to render distinct elements only in an array with duplicates

The expression language is a subset of JavaScript, so you can usually start by looking for JavaScript-based solutions.

In this case, take a look at this post:

The first answer has the simplest solution. The only change you have to make is to convert the callback function to use the arrow-function syntax, like so:

$arr.filter((item, pos, a) => a.indexOf(item) == pos)