JavaScript (ES2026) reference · Array Methods

JavaScript Array join() Method

Join all elements into one string, separated by commas or by a separator you choose.

JavaScript (ES2026) Since ES1

Syntax

array.join(separator)

Parameter	Description
`separator` optional	Text between elements. Default: `","`

A string.

Different separatorsTry it yourself

const words = ["red", "green", "blue"];
console.log(words.join(), words.join(" - "), words.join(""));

Output

red,green,blue red - green - blue redgreenblue

null and undefined become emptyTry it yourself

console.log([1, null, undefined, 4].join("-"));

Output

1---4

Version	Change
JavaScript ES1	Added

array.toString() · Return a string of the array's elements separated by commas. Called automatically when an array is used as text.
array.concat() · Return a new array that joins this array with other arrays or values. The original arrays are not changed.
JavaScript Arrays · tutorial
JavaScript Strings · tutorial