JavaScript Join

What is the Join() method in JavaScript?

In JavaScript, the join() method is used to join the elements of an array into a string. The elements of the string will be separated by a specific separator and its default value is comma(,).

In simple words, with the use of the join method, we can create and return a new string by concatenating all of the elements in this array, which is the specified separator string.

The JavaScript array join() method combines all the elements of an array into a string and returns a new string. We can use any type of separator to separate given array elements.

Basically, the JavaScript array join() is a method provided by JavaScript that takes an array as input and returns a string that consists of all the elements of the array joined by a separator.

The separator is an optional parameter as the default value is comma(,). This means all the elements present in the array will be joined. With the use of this method, we cannot join specific elements in the array.

Syntax

Let's see the syntax of the join() method:

Parameter

This method accepts a single parameter, as mentioned in the above example:

Separator: In the join() method, the separator is an optional parameter. It represents the separator used between array elements.

Return value

It is a string with all array elements joined. Suppose if an array length is 0, then it will return the empty string. And if the array is null or undefined, then it will throw an error that cannot read properties of undefined or cannot read properties of null for the input array whose value is set as undefined or null, respectively.

How does the JavaScript join() method work?

In JavaScript, the join method or function works by combining the elements of an array or arrays, and it stores a string value. It mainly works with the help of only one parameter, "separator1".

The join() method works mostly with the ECMAScript 1. It basically works only for different types of versions for different browsers. In JavaScript, the join() method can work for Chrome 1.0, Internet Explorer 5.5 version, Firefox 1.0 version, All Safari browser versions and all the Opera browser versions, etc.

Examples

Let's take some examples of the array join() method in JavaScript:

Joining an array of four different ways

Let us create an array and join it using four different ways

Output:

 
Ruby,Python,JavaScript,C#
RubyPythonJavaScriptC#
Ruby + Python + JavaScript + C#
Ruby,  Python,  JavaScript,  C#     

Explanation

In the above example, we have used four different ways to join the array, such as using the default separator, using an empty string, using a plus symbol, and using a comma followed by a space.

Joining an array-like object

In JavaScript, the array joins we can join an array-like object by calling function.prototype.call on Array.prototype.join. The elements in the nested array are also joined.

Output:

 
Name, Age, Gender, S,true, 20, Male   

Explanation

In the above example, we can see the elements in both the nested arrays are also joined.

Example

Output:

 
Red, Green, Blue, Yellow, Purple
1 - 2 - 3 - 4 - 5
John (30), Jane (25), Bob (40)
Hello | World |  Foo | Bar Baz   

Conclusion

The `join()` method in JavaScript is used to combine the elements of an array into a string and then return that resulting string. The input for this method is an array, and the output is a string. It doesn't alter the original array. If a separator is provided, the elements of the array are separated using the specified separator. If no separator is provided, a comma is used as the default separator for the `join()` method in JavaScript.