JS: Array.prototype.join

• myArray.join () → join array elements to string, using comma ",".
• myArray.join (seperator_string) → use seperator_string between elements.

const arr = [3, 4, 5];

console.log ( arr.join () === "3,4,5" ); // true

console.log ( arr.join ( "-" ) === "3-4-5" ); // true

[see JS: Array.prototype.toString]