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Javascript Array Join Example | Array.prototype.join() Tutorial


Javascript Array Join Example | Array.prototype.join() Tutorial is today’s leading topic. The join() method creates and returns the new string by concatenating all of the elements of the array. The join() method joins the items of the array into the string and returns that string. The specified separator will separate the array items. The default separator is a comma (,).

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Javascript Array Join Example

The syntax for the join() method is the following.


The separator is an optional parameter. By default, a separator is a comma.

A simple example is the following.

// app.js

let apps = ["Instagram", "Facebook", "Messanger"];
let fb = apps.join();


So, the output is following.


Javascript Array Join Example | Array.prototype.join() Tutorial

So, it returns a comma separated string. We did not pass any parameter to the join() function that is why it has returned the comma separated string.

// app.js

let apps = ["Instagram", "Facebook", "Messanger"];
let fb = apps.join('_');


It will return the underscore separated string.

So, an Array.join() function is used to join all the items of an array together into a string.

If an element is undefined or null, it is converted to the empty string. So If an array.length is 0, the empty string is returned.

Joining an array of four different ways

The following example is an array, with three elements, then joins the array four times: using the default separator, then a comma and space, then a plus and an empty string.

let suits = ['Harvey', 'Mike', 'Louis'];
suits.join();      // 'Harvey,Harvey,Louis'
suits.join(', ');  // 'Harvey, Harvey, Louis'
suits.join(' + '); // 'Harvey + Harvey + Louis'
suits.join('');    // 'HarveyHarveyLouis'

Joining an array-like object

The following example joins array-like object (arguments), by calling on Array.prototype.join.

// app.js

function aros(a, b, c) {
  let data =;
aros(21, 'acme', false);


Javascript Array Join Example

Finally, Javascript Array Join Example | Array.prototype.join() Tutorial is over.

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