mdn .join code example
Example 1: javascript join array
var array = ["Joe", "Kevin", "Peter"];
array.join(); // "Joe,Kevin,Peter"
array.join("-"); // "Joe-Kevin-Peter"
array.join(""); // "JoeKevinPeter"
array.join(". "); // "Joe. Kevin. Peter"
Example 2: concat js mdn
const array1 = ['a', 'b', 'c'];
const array2 = ['d', 'e', 'f'];
const array3 = array1.concat(array2);
console.log(array3);
// expected output: Array ["a", "b", "c", "d", "e", "f"]