JSFiddle - React, Tailwind, and code Playground

JavaScript

var arr = [1,2,3,4,4,4,4,4,5,6,6,6]

   // using reduce function of array
    Array.prototype.unique = function() {
        return this.reduce(function(previousValue, current) {
            if (previousValue.indexOf(current) < 0) {
                previousValue.push(current);
            }
            return previousValue;
        }, []);
    }

    console.log(arr.unique());

    // using filter
    var filteredArray= arr.filter(function(element, index, self) {
        return index == self.indexOf(element);
    });

    console.log(filteredArray);