Key Points:

• Damn, array methods are pretty powerful!
• An array is a special type of variable, an ordered collection of items (strings, numbers, or other things)
• Array indexes start with 0. [0] is the first element. [1] is the second element.
• Arrays allow us to deal with a large quantity of strings and numbers.
• Array methods allow us to manipulate arrays.

Arrays

This is how we declare an array:

const cars = ['Saab', 'Volvo', 'BMW']; 

Arrays are also unaffected by spaces and line breaks:

const cars = [   'Saab',   'Volvo',   'BMW' ]; 

Change an Array Element

We can target a specific element by its index and change it:

const cars = ['Saab','Volvo', 'BMW']; cars [0] = 'Toyota'; 

Accessing the First Array Element

const fruits = ['Banana', 'Orange', 'Apple', 'Mango']; fruits[0]; 

Accessing the Last Array Element

const fruits = ['Banana', 'Orange', 'Apple', 'Mango']; fruits[fruits.length - 1]; 

fruits.length gives us the number of elements in the array. In the case, there are 4 elements. However, the 4th index in this array is non-existent since the indexes are from 0-3. Therefore, we must subtract 1 to access the last array element.

Adding Array Elements

const fruits = ['Banana', 'Orange', 'Apple', 'Mango']; fruits.push('Kiwi'); 

Difference Between Arrays and Objects

Arrays are a type of object. However, the difference is that array items are indexed with numbers, whereas objects are indexed with names.

Array Methods

toString()

Converts an array to a string of (comma separated) array values:

const fruits = ['Banana', 'Orange', 'Apple', 'Mango']; fruits.toString() // Banana,Orange,Apple,Mango; 

join()

Behaves like toString() but we can specify a separator:

const fruits = ['Banana', 'Orange', 'Apple', 'Mango']; fruits.join(', '); // 'Banana', 'Orange', 'Apple', 'Mango' 

pop()

Popping in Javascript means taking out elements. Think of it like “popping” out elements from an array. This method “pops” out the last element:

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

push()

Pushing in Javascript means adding element. Think of it like “pushing” in a new element into an existing array. This method pushes a new element to the end of the array:

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

shift()

Similar to popping, but works on the first element instead of the last:

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

unshift()

Similar to pushing, but adds elements to the beginning instead of end of array:

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

concat()

Allows us to combine (concatenate) multiple arrays together:

const arr1 = ['Apple', 'Microsoft', 'Amazon']; const arr2 = ['Netflix', 'Google', 'Facebook'];  arr1.concat(arr2); // ['Apple', 'Microsoft', 'Amazon', 'Netflix', 'Google', 'Facebook']  

We can combine as many arrays as we want:

const arr1 = ['Apple', 'Microsoft', 'Amazon']; const arr2 = ['Netflix', 'Google', 'Facebook']; const arr3 = ['Tesla', 'Samsung', 'Huawei'];  arr1.concat(arr2, arr3); // ['Apple', 'Microsoft', 'Amazon', 'Netflix', 'Google', 'Facebook', 'Tesla', 'Samsung', 'Huawei'] 

splice()