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
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
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
fruits.pop(); // Removes the last element ("Mango") from fruits
The pop() method returns the value that was "popped out":
Example
var x = fruits.pop(); // the value of x is "Mango"
Pushing
The push() method adds a new element to an array (at the end):
Example
fruits.push("Kiwi"); // Adds a new element ("Kiwi") to fruits
The push() method returns the new array length:
Example
var x = fruits.push("Kiwi"); // the value of x is 5
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
fruits.shift(); // Removes the first element "Banana" from fruits
The unshift() method adds a new element to an array (at the beginning), and "unshifts" older elements:
Example
fruits.unshift("Lemon"); // Adds a new element "Lemon" to fruits
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
fruits[0] = "Kiwi"; // Changes the first element of fruits to "Kiwi"
The length property provides an easy way to append a new element to an array:
Example
fruits[fruits.length] = "Kiwi"; // Appends "Kiwi" to fruit
Deleting Elements
Since JavaScript arrays are objects, elements can be deleted by using the JavaScript operator delete:
Example
delete fruits[0]; // Changes the first element in fruits to undefined
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
fruits.splice(2, 0, "Lemon", "Kiwi");
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
fruits.splice(0, 1); // Removes the first element of fruits
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 myBoys = ["Emil", "Tobias","Linus"];
var myChildren = myGirls.concat(myBoys); // Concatenates (joins) myGirls and myBoys
The concat() method can take any number of array arguments:
Example
var arr2 = ["Emil", "Tobias","Linus"];
var arr3 = ["Robin", "Morgan"];
var myChildren = arr1.concat(arr2, arr3); // Concatenates arr1 with arr2 and arr3
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 citrus = fruits.slice(1);
Array indexes start with 0. [0] is the first array element, [1] is the second, [2] is the third ...
This example slices out a part of an array starting from array element 3 ("Apple"):
Example
var citrus = fruits.slice(3);
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 citrus = fruits.slice(1, 3);
If the end argument is omitted, like in the first examples, the slice() method slices out the rest of the array.
Example
var citrus = fruits.slice(2);
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
document.getElementById("demo").innerHTML = fruits;
Example
document.getElementById("demo").innerHTML = fruits.valueOf();
Example
document.getElementById("demo").innerHTML = fruits.toString();
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 »
