Array Methods

Arrays have many methods that perform different task.

1. .push() Method

.push() allows us to add items to the end of an array.

For example, we add numbers 4 and 5 to the array

const numbers = [1, 2, 3];

numbers.push(4, 5);

console.log(numbers);
// Output: [1, 2, 3, 4, 5]

2. .pop() Method

.pop() removes the last item of an array.

const numbers = [1, 2, 3];

const removed = numbers.pop();

console.log(numbers);
// Output: [1, 2]

console.log(removed);
// Output: 3

3. .shift() Method

shift() method removes the first element from an array and returns that removed element. This method changes the length of the array.

const array1 = [1, 2, 3, 4, 5];

const firstElement = array1.shift();

console.log(array1);
// Output: [2, 3, 4, 5]

console.log(firstElement);
// Output: 1

4. .unshift() method

The unshift() method adds one or more elements to the beginning of an array and returns the new length of the array.

const array1 = [1, 2, 3];

console.log(array1.unshift(4, 5));
// Output: 5

console.log(array1);
// Output: Array [4, 5, 1, 2, 3]

5. .splice()

splice() method removes or replaces existing elements and/or adds new elements in place.

array.splice(indexToStart, numberOfIndices, "stringToAdd");

For example:

const months = ["Jan", "March", "April", "May"];

months.splice(1, 0, "Feb");
// inserts at index 1

console.log(months);
// Output: Array ["Jan", "Feb", "March", "April", "May"]

6. .concat()

concat() method creates a new array by merging existing arrays.

let a = [1, 2];
let b = [3, 4, 5];
let c = a.concat(b);

7. .slice()

slice() method slices out a piece of an array into a new array from start to end (end not included).

let array1 = [0, 1, 2, 3, 4, 5];
let num = array1.slice(1, 4);

// Output: [1, 2, 3]

8. reverse()

reverse() method reverses the elements in an array. arr.reverse();

9. Check if it’s an array

To check if something is an array, we use Array.isArray() method

const numbers = [1, 2, 3];
console.log(Array.isArray(numbers)); // true
console.log(Array.isArray("hello")); // false because it's a string

10. Check the index

To check the index of an item in an array, we use indexOf().

const names = ["Anna", "Pete", "Jane", "Luna"];
console.log(names.indexOf("Jane")); // 2