Javascript Array join()

The join() method returns a new string by concatenating all of the elements in an array, separated by a specified separator.


let message = ["JavaScript", "is", "fun."];

// join all elements of array using space
let joinedMessage = message.join(" ");

// Output: JavaScript is fun.

join() Syntax

The syntax of the join() method is:


Here, arr is an array.

join() Parameters

The join() method takes in:

  • separator (optional) - A string to separate each pair of adjacent elements of the array. By default, it is comma ,.

join() Return Value

  • Returns a String with all the array elements joined by separator.


  • The join() method does not change the original array.
  • Elements like undefined, null, or empty array have an empty string representation.

Example: Using join() method

var info = ["Terence", 28, "Kathmandu"];

var info_str = info.join(" | ");
// join() does not change the original array console.log(info); // [ 'Terence', 28, 'Kathmandu' ] // join() returns the string by joining with separator console.log(info_str); // Terence | 28 | Kathmandu // empty argument = no separator var collection = [3, ".", 1, 4, 1, 5, 9, 2];
console.log(collection.join("")); // 3.141592
var random = [44, "abc", undefined];
console.log(random.join(" and ")); // 44 and abc and


[ 'Terence', 28, 'Kathmandu' ]
Terence | 28 | Kathmandu
44 and abc and 

Here, we can see that the join() method converts all the array elements into a string and separates each element by the specified separator.

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