JSFiddle - React, Tailwind, and code Playground

JavaScript

function remove_duplicates(array_){
	var ret_array = new Array();
	for (var a = array_.length - 1; a >= 0; a--) {
		for (var b = array_.length - 1; b >= 0; b--) {
			if(array_[a] == array_[b] && a != b){
				delete array_[b];
			}
		};
	    if(array_[a] != undefined)
	        ret_array.push(array_[a]);
	};
	return ret_array;
}
console.log(remove_duplicates(Array(1,1,1,2,2,2,3,3,3)));