JavaScript Array Methods
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:
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:
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
Try it Yourself »
The pop() method returns the value that was "popped out":
Example
const fruits = ["Banana", "Orange", "Apple", "Mango"];
let x = fruits.pop(); // x = "Mango"
Try it Yourself »
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
Try it Yourself »
The push() method returns the new array length:
Example
const fruits = ["Banana", "Orange", "Apple", "Mango"];
let x =
fruits.push("Kiwi"); // x = 5
Try it Yourself »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
Try it Yourself »
The shift() method returns the value that was "shifted out":
Example
const fruits = ["Banana", "Orange", "Apple", "Mango"];
let x =
fruits.shift(); // x = "Banana"
Try it Yourself »
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
Try it Yourself »
The unshift() method returns the new array length.
Example
const fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.unshift("Lemon");
// Returns 5
Try it Yourself »
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"
Try it Yourself »
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
Try it Yourself »
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
Try it Yourself »
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
const 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.
The splice() method returns an array with the deleted items:
Example
const fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.splice(2, 2, "Lemon", "Kiwi");
Try it Yourself »
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
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.
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);
Try it Yourself »
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);
Try it Yourself »
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");
Try it Yourself »
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);
Try it Yourself »
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);
Try it Yourself »
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);
Try it Yourself »
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);
Try it Yourself »
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();
Try it Yourself »
Example
const fruits = ["Banana", "Orange", "Apple", "Mango"];
document.getElementById("demo").innerHTML = fruits;
Try it Yourself »
All JavaScript objects have a toString() method.
Finding Max and Min Values in an Array
There are no built-in functions for finding the highest or lowest value in a JavaScript array.
You will learn how you solve this problem in the next chapter of this tutorial.
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.
