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JavaScript Array Methods


The strength of JavaScript arrays lies in the array methods.


Converting Arrays to Strings

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

Example

var 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

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

Result

Banana * Orange * Apple * Mango
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.


Popping

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

Example

var fruits = ["Banana", "Orange", "Apple", "Mango"];
var x = fruits.pop();      // the value of x is "Mango"
Try it Yourself »

Pushing

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

Example

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.push("Kiwi");       //  Adds a new element ("Kiwi") to fruits
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The push() method returns the new array length:

Example

var fruits = ["Banana", "Orange", "Apple", "Mango"];
var x = fruits.push("Kiwi");   //  the value of x is 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

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

Array indexes start with 0. [0] is the first array element, [1] is the second, [2] is the third ...

Example

var 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

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits[fruits.length] = "Kiwi";          // Appends "Kiwi" to fruit
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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
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Using delete may leave undefined holes in the array. Use pop() or shift() 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");
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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.


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
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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.


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
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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
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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

var fruits = ["Banana", "Orange", "Lemon", "Apple", "Mango"];
var 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

var fruits = ["Banana", "Orange", "Lemon", "Apple", "Mango"];
var 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

var fruits = ["Banana", "Orange", "Lemon", "Apple", "Mango"];
var 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

var fruits = ["Banana", "Orange", "Lemon", "Apple", "Mango"];
var citrus = fruits.slice(2);
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The valueOf() Method

The valueOf() method is the default behavior for an array. It converts an array to a primitive value.

JavaScript will automatically convert an array to a string when a primitive value is expected.

Because of this, all these examples will produce the same result:

Example

var fruits = ["Banana", "Orange", "Apple", "Mango"];
document.getElementById("demo").innerHTML = fruits;
Try it Yourself »

Example

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

var fruits = ["Banana", "Orange", "Apple", "Mango"];
document.getElementById("demo").innerHTML = fruits.toString();
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All JavaScript objects have a valueOf() and a toString() method.


Sorting Arrays

Sorting arrays are covered in the next chapter of this tutorial.


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.


Test Yourself with Exercises!

Exercise 1 »  Exercise 2 »  Exercise 3 »  Exercise 4 »  Exercise 5 »