JS: Array.prototype.join

By Xah Lee. Date: 2017-03-09. Last updated: 2024-04-09.

arrayX.join()

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

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

Nested array are flattened:

[3, 4, [3, 4]].join() === "3,4,3,4"

array containing data objects:

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

arrayX.join(seperatorString)

Use seperatorString between elements.

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