JavaScript Array Methods

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Converting Arrays To Strings

The JavaScript method toString() converts an array to a string of (comma separated) array values.

Example

const fruits = ["Banana", "Orange", "Apple", "Mango"];
document.getElementById("demo").innerHTML = fruits.toString();

Result:

Banana,Orange,Apple,Mango

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The join() method also joins all array elements into a string.

It behaves just like toString(), but in addition you can specify the separator:

Example

const fruits = ["Banana", "Orange", "Apple", "Mango"];
document.getElementById("demo").innerHTML = fruits.join(" * ");

Result:

Banana * Orange * Apple * Mango

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Popping And Pushing

When you work with arrays, it is easy to remove elements and add new elements.

This is what popping and pushing is:

Popping items out of an array, or pushing items into an array.

Popping

The pop() method removes the last element from an array:

Example

const fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.pop(); // Removes "Mango" from fruits

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The pop() method returns the value that was "popped out":

Example

const fruits = ["Banana", "Orange", "Apple", "Mango"];
let x = fruits.pop(); // x = "Mango"

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Pushing

The push() method adds a new element to an array (at the end):

Example

const fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.push("Kiwi"); // Adds "Kiwi" to fruits

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The push() method returns the new array length:

Example

const fruits = ["Banana", "Orange", "Apple", "Mango"];
let x = fruits.push("Kiwi"); // x = 5

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Shifting Elements

Shifting is equivalent to popping, working on the first element instead of the last.

The shift() method removes the first array element and "shifts" all other elements to a lower index.

Example

const fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.shift(); // Removes "Banana" from fruits

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The shift() method returns the value that was "shifted out":

Example

const fruits = ["Banana", "Orange", "Apple", "Mango"];
let x = fruits.shift(); // x = "Banana"

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The unshift() method adds a new element to an array (at the beginning), and "unshifts" older elements:

Example

const fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.unshift("Lemon"); // Adds "Lemon" to fruits

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The unshift() method returns the new array length.

Example

const fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.unshift("Lemon"); // Returns 5

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Changing Elements

Array elements are accessed using their index number:

Array indexes start with 0:

[0] is the first array element
[1] is the second
[2] is the third ...

Example

const fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits[0] = "Kiwi"; // Changes the first element of fruits to "Kiwi"

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The length property provides an easy way to append a new element to an array:

Example

const fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits[fruits.length] = "Kiwi"; // Appends "Kiwi" to fruits

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Deleting Elements

Since JavaScript arrays are objects, elements can be deleted by using the JavaScript operator delete:

Example

const fruits = ["Banana", "Orange", "Apple", "Mango"];
delete fruits[0]; // Changes the first element in fruits to undefined

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Using delete may leave undefined holes in the array. Use pop() or shift() instead.

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Splicing An Array

The splice() method can be used to add new items to an array:

Example

const fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.splice(2, 0, "Lemon", "Kiwi");

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The first parameter (2) defines the position where new elements should be added (spliced in).

The second parameter (0) defines how many elements should be removed.

The rest of the parameters ("Lemon" , "Kiwi") define the new elements to be added.

The splice() method returns an array with the deleted items:

Example

const fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.splice(2, 2, "Lemon", "Kiwi");

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Using splice() to Remove Elements

With clever parameter setting, you can use splice() to remove elements without leaving "holes" in the array:

Example

const fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.splice(0, 1); // Removes the first element

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The first parameter (0) defines the position where new elements should be added (spliced in).

The second parameter (1) defines how many elements should be removed.

The rest of the parameters are omitted. No new elements will be added.

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Merging (Concatenating) Arrays

The concat() method creates a new array by merging (concatenating) existing arrays:

Example (Merging Two Arrays)

const myGirls = ["Cecilie", "Lone"];
const myBoys = ["Emil", "Tobias", "Linus"];

// Concatenate (join) myGirls and myBoys
const myChildren = myGirls.concat(myBoys);

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The concat() method does not change the existing arrays. It always returns a new array.

The concat() method can take any number of array arguments:

Example (Merging Three Arrays)

const arr1 = ["Cecilie", "Lone"];
const arr2 = ["Emil", "Tobias", "Linus"];
const arr3 = ["Robin", "Morgan"];
const myChildren = arr1.concat(arr2, arr3);

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The concat() method can also take strings as arguments:

Example (Merging an Array with Values)

const arr1 = ["Emil", "Tobias", "Linus"];
const myChildren = arr1.concat("Peter");

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Slicing An Array

The slice() method slices out a piece of an array into a new array.

This example slices out a part of an array starting from array element 1 ("Orange"):

Example

const fruits = ["Banana", "Orange", "Lemon", "Apple", "Mango"];
const citrus = fruits.slice(1);

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The slice() method creates a new array. It does not remove any elements from the source array.

This example slices out a part of an array starting from array element 3 ("Apple"):

Example

const fruits = ["Banana", "Orange", "Lemon", "Apple", "Mango"];
const citrus = fruits.slice(3);

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The slice() method can take two arguments like slice(1, 3).

The method then selects elements from the start argument, and up to (but not including) the end argument.

Example

const fruits = ["Banana", "Orange", "Lemon", "Apple", "Mango"];
const citrus = fruits.slice(1, 3);

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If the end argument is omitted, like in the first examples, the slice() method slices out the rest of the array.

Example

const fruits = ["Banana", "Orange", "Lemon", "Apple", "Mango"];
const citrus = fruits.slice(2);

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Automatic ToString()

JavaScript automatically converts an array to a comma separated string when a primitive value is expected.

This is always the case when you try to output an array.

These two examples will produce the same result:

Example

const fruits = ["Banana", "Orange", "Apple", "Mango"];
document.getElementById("demo").innerHTML = fruits.toString();

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Example

const fruits = ["Banana", "Orange", "Apple", "Mango"];
document.getElementById("demo").innerHTML = fruits;

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All JavaScript objects have a toString() method.

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Previous Next

JavaScript Array Methods

Converting Arrays To Strings

Example

Example

Popping And Pushing

Popping

Example

Example

Pushing

Example

Example

Shifting Elements

Example

Example

Example

Example

Changing Elements

Example

Example

Deleting Elements

Example

Splicing An Array

Example

Example

Using splice() to Remove Elements

Example

Merging (Concatenating) Arrays

Example (Merging Two Arrays)

Example (Merging Three Arrays)

Example (Merging an Array with Values)

Slicing An Array

Example

Example

Example

Example

Automatic ToString()

Example

Example

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