JS: Array.prototype.join

• myArray.join ()
• myArray.join (seperator_string)

Convert to string, with seperator_string in between.

By default, seperator_string is a comma ",".

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]

Reference

ECMAScript® 2016 Language Specification#sec-array.prototype.join