JavaScript: Array.prototype.join

arrayX.join()

Join array elements to string, using comma ",".

console.log([3, 4, 5].join() === "3,4,5");

Nested array are flattened:

// example of join nested array
console.log([3, 4, [3, 4]].join() === "3,4,3,4");

array containing data objects:

// array containing data objects
const xx = [3, { k: 4 }];
console.log(xx.join() === "3,[object Object]");

arrayX.join(seperatorString)

Use seperatorString between elements.

console.log([3, 4, 5].join("-") === "3-4-5");