Array.prototype.join()

const elements = ["Fire", "Air", "Water"];

console.log(elements.join());
// Expected output: "Fire,Air,Water"

console.log(elements.join(""));
// Expected output: "FireAirWater"

console.log(elements.join("-"));
// Expected output: "Fire-Air-Water"

var a = ["Wind", "Rain", "Fire"];
a.join(); // 'Wind,Rain,Fire'
a.join(", "); // 'Wind, Rain, Fire'
a.join(" + "); // 'Wind + Rain + Fire'
a.join(""); // 'WindRainFire'

function f(a, b, c) {
  var s = Array.prototype.join.call(arguments);
  console.log(s); // '1,a,true'
}
f(1, "a", true);
//expected output: "1,a,true"