# Array Methods in JavaScript # What is Array # Array Methods **length** **push** **slice** **splice** **concatenation** **fill** **includes** **indexOf** **isArray()** **join** **lastindexOf** **map** **pop** **shift** **sort** **unshift** **converting to array** # What is Array An array is an object that can store multiple values in one variable. The array can be represented by a square bracket\[\]. All the elements in the array can be separated by a comma(,). And the indexing of the array always starts from 0. **Syntax:** `let array[1, 2, 3];` **Example:** ```javascript let names = ['John', 'Max', 'Sam']; console.log(names); ``` **Output:** ```javascript ['John', 'Max', 'Sam'] ``` # Array Methods Array methods are functions built-in into JavaScript that we can apply to our arrays Each method has a unique function that performs a change or calculation to our array and saves us from writing common functions. There are a lot of array methods to use its function. **length** **push** **slice** **splice** **concatenation** **fill** **includes** **indexOf** **isArray()** **join** **lastindexOf** **map** **pop** **shift** **sort** **unshift** **converting to array** # length The length method defines the number of elements in that array. **Syntax:** `array.length` **Example:** ```javascript const fruits = ['Apple', 'Banana', 'Grapes', 'Oranges']; console.log(fruits.length); ``` **Output:** ```javascript 4 ``` In the above example, the length of array elements is 4. # Push Using the push method you can insert new values inside the array at the end. **Syntax:** `array.push(element1,element2,....,elementn);` **Example:** ```javascript let cars = ['Volvo', 'BMW', 'Swift', 'Baleno']; cars.push('Duster'); console.log(cars); ``` **Output:** ```javascript [ 'Volvo', 'BMW', 'Swift', 'Baleno', 'Duster' ] ``` In the above example using the push() method Duster name is added to the array at the end. # Slice In the slice method, the last value is not included in the array. **Syntax:** `arr.slice([start], [end])` **Example:** ```javascript const animals = ['ant', 'bison', 'camel', 'duck', 'elephant']; console.log(animals.slice(2, 4)); ``` **Output:** ```javascript ['camel', 'duck'] ``` In the above example, at indexing point 2 camel is there and at indexing 4 elephant is there but in the slice, the last value is not included that's why duck is printed in the output. 2 - start inserting from this index 4 - end index # Splice To insert value inside an array. **Syntax:** `arr.splice([start], [end])` **Example:** ```javascript const months = ['Jan', 'March', 'April', 'June']; months.splice(1, 0, 'Feb'); console.log(months); ``` **Output:** ```javascript ['Jan', 'Feb', 'March', 'April', 'June'] ``` In the above example, the Feb is added at 1 indexing position in the array. # Concatenation It can connect two or more arrays. **Syntax:** `array1.conact(array2)` **Example:** ```javascript const array1 = ['a', 'b', 'c']; const array2 = ['d', 'e', 'f']; const array3 = array1.concat(array2); console.log(array3); ``` **Output:** ```javascript [ 'a', 'b', 'c', 'd', 'e', 'f' ] ``` In the above example, array1 and array2 are connected. # fill Using the fill method you can fill the elements in an array. **Syntax:** `arr.fill(value, start, end)` **Example:** ```javascript let array4 = [1, 2, 3, 4]; console.log(array4.fill(0, 2, 4)); ``` **Output:** ```javascript [1, 2, 0, 0] ``` In the above example fill 0 from position 2 to position 4. # includes The include method returns true if the specified element is there in the array otherwise it returns false. **Syntax:** `array.includes(value)` **Example:** ```javascript let array1 = ['cat', 'dog', 'cow']; console.log(array1.includes('cat')); ``` **Output:** ```javascript true ``` In the above example, the 'cat' is included in that array that's why the output will give true value. # indexOf It can define the index of a given element of an array. If it is not present in that array then it will give a -1 value. **Syntax:** `indexOf(value)` **Example:** ```javascript let array2 = ['Alex', 1, 2, 3]; console.log(indexOf('Alex')); ``` **Output:** ```javascript 0 ``` In the above example, Alex is given at 0 indexing. # isArray It returns true if an element is an array otherwise it returns false. It can check only is there the value passed is in an array or not. **Syntax:** `array.isArray(value)` **Example:** ```javascript let array5 = [4, 5, 6, 7]; console.log(Array.isArray(5)); ``` **Output:** ```javascript true ``` In the above example, the 5 is in that array that's why the output will give a true value. # join It joins the elements of an array as a string. And it is separated by a comma or separate string. **Syntax:** `join()` **Example:** ```javascript let array6 = [1, 2, 3, 4]; let names = array6.join(' 5 '); console.log(var); ``` **Output:** ```javascript 1 5 2 5 3 5 4 ``` In the above example, the 5 can join every element of a given array. # lastindexOf It searches the specified element in an array and returns the index of the last match. **Syntax:** `array.lastIndexOf(element,index)` **Example:** ```javascript const animals = ['Dodo', 'Tiger', 'Penguin', 'Dodo']; console.log(animals.lastIndexOf('Dodo')); ``` **Output:** ```javascript 3 ``` In the above example, 'Dodo's name's last index is 3 that's why it will give output 3. # map It creates a new array and it can call the functions. **Syntax:** `array.map(callback(element ,index))` **Example:** ```javascript const maths = [1, 4, 9, 16]; console.log = (maths.map(Math.sqrt)); ``` **Output:** ```javascript [1, 2, 3, 4] ``` In the above example math.sqrt function call and it will give the square root of these elements. # pop It removes the last element from an array. **Syntax:** `pop()` **Example:** ```javascript let array8 = [8, 9, 10, 11, 12]; console.log(array8.pop()); console.log(array8); ``` **Output:** ```javascript [8, 9, 10, 11] ``` In the above example, the 12 is removed from that array by using the pop method. # reverse It reverses the elements of the given array. **Syntax:** `reverse()` **Example:** ```javascript let array9 = [1, 2, 3, 4, 5]; console.log(array9.reverse()); ``` **Output:** ```javascript [5, 4, 3, 2, 1] ``` In the above example, the array elements will give in reverse order. # shift It removes the first element from an array. **Syntax:** `shift()` **Example:** ```javascript let maths = [5, 1, 2, 3, 4]; console.log(maths.shift()); ``` **Output:** ```javascript [1, 2, 3, 4] ``` In the above example, the 5 is removed because it is at the first position in an array. # sort It returns the element of the given array in sorted order by default it is in ascending order. **Syntax:** `sort()` **Example:** ```javascript let sort = [5, 3, 1, 4, 2]; console.log(sort); ``` **Output:** ```javascript [1, 2, 3, 4, 5] ``` In the above example, the array is sorted properly. # unshift It adds elements at the beginning of an array. **Syntax:** `unshift()` **Example:** ```javascript let fruit = ['Grapes', 'Banana', 'Apple', 'Oranges']; fruit.unshift('Mango', 'Pineapple'); console.log(fruit); ``` **Output:** ```javascript 'Mango', 'Pineapple', 'Grapes', 'Banana', 'Apple', 'Oranges' ``` In the above example, the Mango and Pineapple fruit names are added at the beginning of an array of elements. # converting to array Converting string to array split() method is used. **Syntax:** `array.split()` **Example:** ```javascript let name = ['Matrix']; let array1 = name.split(''); console.log(array1); ``` **Output:** ```javascript ['M', 'a', 't', 'r', 'i', 'x'] ``` In the above example, the Matrix is a string and it is converted into an array by using the split() method.