Built the join method using JavaScript

join.js

"use strict";

var _ = {
	join: (array, separator = ',') => {
		var newString = array.toString();
		if (separator) {
			var replaced = newString.replace(",", separator);
		}
		console.log(replaced);
	}
}

const value = _.join(["hello", "goodbye"], "...")

console.log(value);