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JavaScript Array Methods


The strength of JavaScript arrays lies in the array methods.


Converting Arrays to Strings

In JavaScript, all objects have the valueOf() and toString() methods.

The valueOf() method is the default behavior for an array. It returns an array as a string:

Example

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

Try it Yourself »

For JavaScript arrays, valueOf() and toString() are equal.

Example

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

Try it Yourself »

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

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

Example

<p id="demo"></p>

<script>
var fruits = ["Banana", "Orange","Apple", "Mango"];
document.getElementById("demo").innerHTML = fruits.join(" * ");
</script>

Try it Yourself »


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.

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

Example

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.pop();              // Removes the last element ("Mango") from fruits

Try it Yourself »

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

Note Remember: [0] is the first element in an array. [1] is the second. Array indexes start with 0.

Example

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.push("Kiwi");       //  Adds a new element ("Kiwi") to fruits

Try it Yourself »

The pop() method returns the string that was "popped out".

The push() method returns the new array length.


Shifting Elements

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

The shift() method removes the first element of an array, and "shifts" all other elements one place down.

Example

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.shift();            // Removes the first element "Banana" from fruits

Try it Yourself »

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

Example

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.unshift("Lemon");    // Adds a new element "Lemon" to fruits

Try it Yourself »

The shift() method returns the string that was "shifted out".

The unshift() method returns the new array length.


Changing Elements

Array elements are accessed using their index number:

Example

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

Try it Yourself »

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

Example

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

Try it Yourself »


Deleting Elements

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

Example

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

Try it Yourself »

Note Using delete on array elements leaves undefined holes in the array. Use pop() or splice() instead.


Splicing an Array

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

Example

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

Try it Yourself »

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.


Using splice() to Remove Elements

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

Example

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

Try it Yourself »

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.


Sorting an Array

The sort() method sorts an array alphabetically:

Example

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.sort();            // Sorts the elements of fruits

Try it Yourself »

The sort() method takes a function as parameter. The function can be used to define the sort method.


Reversing an Array

The reverse() method reverses the elements in an array.

You can use it to sort an array in descending order:

Example

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.sort();            // Sorts the elements of fruits
fruits.reverse();         // Reverses the order of the elements

Try it Yourself »


Numeric Sort

The sort() method cannot be used on a number array, because it sorts alphabetically (25 is bigger than 100).

You can fix this by providing a function that returns -1, 0, or 1:

Example

var points = [40, 100, 1, 5, 25, 10];
points.sort(function(a, b){return a-b});

Try it Yourself »

Use the same trick to sort an array descending:

Example

var points = [40, 100, 1, 5, 25, 10];
points.sort(function(a, b){return b-a});

Try it Yourself »

Calling function(a, b) returns -1, 0, or 1, depending on the values of a and b.

The arguments are provided by the sort() method when it compares two values.

Example: When comparing 40 and 100, the sort() method calls function(40,100).


Find the Highest (or Lowest) Value

How to find the highest value in an array?

Example

var points = [40, 100, 1, 5, 25, 10];
points.sort(function(a, b){return b-a});
// now points[0] contains the highest value

Try it Yourself »

And the lowest:

Example

var points = [40, 100, 1, 5, 25, 10];
points.sort(function(a, b){return a-b});
// now points[0] contains the lowest value

Try it Yourself »


Joining Arrays

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

Example

var myGirls = ["Cecilie", "Lone"];
var myBoys = ["Emil", "Tobias","Linus"];
var myChildren = myGirls.concat(myBoys);     // Concatenates (joins) myGirls and myBoys

Try it Yourself »

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

Example

var arr1 = ["Cecilie", "Lone"];
var arr2 = ["Emil", "Tobias","Linus"];
var arr3 = ["Robin", "Morgan"];
var myChildren = arr1.concat(arr2, arr3);     // Concatenates arr1 with arr2 and arr3

Try it Yourself »


Slicing an Array

The slice() method slices out a piece of an array:

Example

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

Try it Yourself »


Complete Array Reference

For a complete reference, go to our Complete JavaScript Array Reference.

The reference contains descriptions and examples of all Array properties and methods.



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