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30-Days-Of-JavaScript
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05_Day/05_day_arrays.md
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@ -35,13 +35,13 @@
## Arrays ## Arrays
In contrast to variables array can store _multiple values_. Each value in an array has an _index_ and each index has _a reference in a memory address_. Each value can be accessed by using their _indexes_. The index of an array starts from _zero_ and the last element is less by one from the length of the array. In contrast to variables, an array can store _multiple values_. Each value in an array has an _index_, and each index has _a reference in a memory address_. Each value can be accessed by using their _indexes_. The index of an array starts from _zero_, and the last element is less by one from the length of the array.
Array is a collection of different data types which are ordered and changeable(modifiable). Allows duplicate element and different data types. An array can be empty or it may have different data type values An array is a collection of different data types which are ordered and changeable(modifiable). An array allows storing duplicate elements and different data types. An array can be empty, or it may have different data type values.
### How to create an empty array ### How to create an empty array
In JavaScript we can create array in different ways. Let us different ways to create an array. In JavaScript, we can create an array in different ways. Let us different ways to create an array.
- Using Array constructor - Using Array constructor
@ -125,7 +125,7 @@ console.log(arr)
### Creating an array using split ### Creating an array using split
As we have seen in earlier section, we can split a string at different position and we can change to an array. Let us see the examples blow. As we have seen in the earlier section, we can split a string at different positions, and we can change to an array. Let us see the examples below.
```js ```js
let js = 'JavaScript' let js = 'JavaScript'
@ -148,7 +148,7 @@ console.log(words)
### Accessing array items using index ### Accessing array items using index
We access each element in an array using their index. An array index start from 0. The picture below show clearly the starting of the index. We access each element in an array using their index. An array index starts from 0. The picture below clearly shows the starting of the index.
![arr index](../images/array_index.png) ![arr index](../images/array_index.png)
@ -247,7 +247,7 @@ console.log(shoppingCart[lastIndex]) // -> Sugar
### Modifying array element ### Modifying array element
An array is mutable(modifiable). Once an array is created we can modify the contents or the array elements. An array is mutable(modifiable). Once an array is created, we can modify the contents of the array elements.
```js ```js
const numbers = [1, 2, 3, 4, 5] const numbers = [1, 2, 3, 4, 5]
@ -283,7 +283,7 @@ console.log(countries)
### Methods to manipulate array ### Methods to manipulate array
There are different methods to manipulate an array. These are some of the available methods to deal with arrays:_Array,length, concat, indexOf, slice, splice, join, toString, includes, lastIndexOf, isArray, fill, push, pop, shift, unshift_ There are different methods to manipulate an array. These are some of the available methods to deal with arrays:_Array, length, concat, indexOf, slice, splice, join, toString, includes, lastIndexOf, isArray, fill, push, pop, shift, unshift_
#### Array Constructor #### Array Constructor
@ -305,13 +305,13 @@ fill: Fill all the array elements with a static value
const arr = Array() // creates an an empty array const arr = Array() // creates an an empty array
console.log(arr) console.log(arr)
const eightXvalues = Array(8).fill('X') // it creates eight element values const eightXvalues = Array(8).fill('X') // it creates eight element values filled with 'X'
console.log(eightXvalues) // ['X', 'X','X','X','X','X','X','X'] console.log(eightXvalues) // ['X', 'X','X','X','X','X','X','X']
const eight0values = Array(8).fill(0) // it creates eight element values const eight0values = Array(8).fill(0) // it creates eight element values filled with '0'
console.log(eight0values) // [0, 0, 0, 0, 0, 0, 0, 0] console.log(eight0values) // [0, 0, 0, 0, 0, 0, 0, 0]
const four4values = Array(4).fill(4) // it creates 4 element values const four4values = Array(4).fill(4) // it creates 4 element values filled with '4'
console.log(four4values) // [4, 4, 4, 4, 4, 4, 4, 4] console.log(four4values) // [4, 4, 4, 4, 4, 4, 4, 4]
``` ```
@ -330,7 +330,7 @@ console.log(thirdList) // [1, 2, 3, 4, 5, 6]
```js ```js
const fruits = ['banana', 'orange', 'mango', 'lemon'] // array of fruits const fruits = ['banana', 'orange', 'mango', 'lemon'] // array of fruits
const vegetables = ['Tomato', 'Potato', 'Cabbage', 'Onion', 'Carrot'] // array of vegetables const vegetables = ['Tomato', 'Potato', 'Cabbage', 'Onion', 'Carrot'] // array of vegetables
const fruitsAndVegetables = fruits.concat(vegetables) const fruitsAndVegetables = fruits.concat(vegetables) // concatinate the two arrays
console.log(fruitsAndVegetables) console.log(fruitsAndVegetables)
``` ```
@ -345,7 +345,7 @@ Length:To know the size of the array
```js ```js
const numbers = [1, 2, 3, 4, 5] const numbers = [1, 2, 3, 4, 5]
console.log(numbers.length) // -> 5 console.log(numbers.length) // -> 5 is the size of the array
``` ```
#### Getting index an element in arr array #### Getting index an element in arr array
@ -361,7 +361,7 @@ console.log(numbers.indexOf(1)) // -> 0
console.log(numbers.indexOf(6)) // -> -1 console.log(numbers.indexOf(6)) // -> -1
``` ```
Check an element if it exist in an array Check an element if it exist in an array.
- Check items in a list - Check items in a list
@ -393,12 +393,12 @@ if(indexOfAvocado!= -1){
#### Getting last index of an element in array #### Getting last index of an element in array
lastIndexOf:Give the position of the last item in the array. If it exist it returns the index else it returns -1. lastIndexOf: It gives the position of the last item in the array. If it exist, it returns the index else it returns -1.
```js ```js
const numbers = [1, 2, 3, 4, 5, 3, 1, 2] const numbers = [1, 2, 3, 4, 5, 3, 1, 2]
console.log(numbers.lastIndexOf(2)) // -7 console.log(numbers.lastIndexOf(2)) // 7
console.log(numbers.lastIndexOf(0)) // -1 console.log(numbers.lastIndexOf(0)) // -1
console.log(numbers.lastIndexOf(1)) // 6 console.log(numbers.lastIndexOf(1)) // 6
console.log(numbers.lastIndexOf(4)) // 3 console.log(numbers.lastIndexOf(4)) // 3
@ -455,7 +455,7 @@ console.log(names.toString()) // Asabeneh,Mathias,Elias,Brook
#### Joining array elements #### Joining array elements
join:To join the elements of the array, the argument passed in the join method will be joined in the array and return as a string. By default it joins with a comma but we can pass different string parameter which can be joined between the items. join: It used to join the elements of the array, the argument passed in the join method will be joined in the array and return as a string. By default, it joins with a comma, but we can pass different string parameter which can be joined between the items.
```js ```js
const numbers = [1, 2, 3, 4, 5] const numbers = [1, 2, 3, 4, 5]
@ -485,7 +485,7 @@ console.log(webTechs.join(' # ')) // "HTML # CSS # JavaScript # React # Redux #
#### Slice array elements #### Slice array elements
Slice: To cut out a multiple items in range. It takes two parameters:starting and ending position. It doesn't include the ending position Slice: To cut out a multiple items in range. It takes two parameters:starting and ending position. It doesn't include the ending position.
```js ```js
const numbers = [1,2,3,4,5] const numbers = [1,2,3,4,5]
@ -498,7 +498,7 @@ Slice: To cut out a multiple items in range. It takes two parameters:starting an
#### Splice method in array #### Splice method in array
Splice: It takes three parameters:Starting position, number of times to be removed and number items to be added. Splice: It takes three parameters:Starting position, number of times to be removed and number of items to be added.
```js ```js
const numbers = [1, 2, 3, 4, 5]; const numbers = [1, 2, 3, 4, 5];
@ -511,7 +511,7 @@ Splice: It takes three parameters:Starting position, number of times to be remov
#### Adding item to an array using push #### Adding item to an array using push
Push: adding item in the end. To add item to the end of an existing array we use the push method Push: adding item in the end. To add item to the end of an existing array we use the push method.
```js ```js
// syntax // syntax
@ -544,7 +544,7 @@ console.log(fruits) // ['banana', 'orange', 'mango', 'lemon', 'apple', 'lime']
#### Removing the end element using pop #### Removing the end element using pop
Pop: Removing item in the end Pop: Removing item in the end.
```js ```js
const numbers = [1, 2, 3, 4, 5] const numbers = [1, 2, 3, 4, 5]
@ -555,7 +555,7 @@ console.log(numbers) // -> [1,2,3,4]
#### Removing an element from the beginning #### Removing an element from the beginning
shift: Removing one array element in the beginning of the array shift: Removing one array element in the beginning of the array.
```js ```js
const numbers = [1, 2, 3, 4, 5] const numbers = [1, 2, 3, 4, 5]
@ -566,7 +566,7 @@ console.log(numbers) // -> [2,3,4,5]
#### Add an element from the beginning #### Add an element from the beginning
unshift: Adding array element in the beginning of the array unshift: Adding array element in the beginning of the array.
```js ```js
const numbers = [1, 2, 3, 4, 5] const numbers = [1, 2, 3, 4, 5]
@ -577,7 +577,7 @@ console.log(numbers) // -> [0,1,2,3,4,5]
#### Reversing array order #### Reversing array order
reverse: reverse the order of an array reverse: reverse the order of an array.
```js ```js
const numbers = [1, 2, 3, 4, 5] const numbers = [1, 2, 3, 4, 5]
@ -591,7 +591,7 @@ console.log(numbers) // [1, 2, 3, 4, 5]
#### Sorting elements in array #### Sorting elements in array
sort: arrange array elements in ascending order. Sort takes a call back function, we wil see how we use sort with call back function in the coming sections. sort: arrange array elements in ascending order. Sort takes a call back function, we will see how we use sort with call back function in the coming sections.
```js ```js
const webTechs = [ const webTechs = [

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