JSFiddle - React, Tailwind, and code Playground

JavaScript

var arrayUnique = function (a) {
    return a.reduce(function (p, c) {
        if (p.indexOf(c) < 0) p.push(c);
        return p;
    }, []);
};
var x = [1, 2, 1, 2];
var y = arrayUnique(x);
console.log(y);