All You Need To Know About Arrays In JavaScript (1)
Tags: javascript, webdev, programming, tutorial
Published: 2022-12-19 22:51:48

**Let's Try To  Know Why We Need Arrays In Programming.**

let's try this scenario we need to write a straightforward program average to five numbers.


```
let  a=1 ,b=2 ,c=3 ,d=4 ,e=5;
let avarage= (a+b+c+d+e) /5
console.log(avarage) // 3
```

**Problems we can figure out**


1. No efficient way to store data 
2. it's so time-consuming 
3. we can not access data in a super easy way 
4. if we use only variables it will be so hard to 
   debug and figure out things.

**Soulution**
 

## Array
Array Syntex
let arrayname= [elemet1 .elemet2 ,elment3 ... ]

characteristics of array data structure 


1. we can store any data type in array like(number, string, boolean, NaN, undefined, other arrays, objects…).
2. Data is stored in an array in a contiguous fashion that makes it easy to 
   access data from the array
```
Let numbers = [1,2,3,4,5] 
```
**Second  less used  way To Create Array**

```
let arr = new array(1,2,3,4,5,6,7,8)
```


**Benefits **
 Data is organized in contagious blocks which are easy to access and modify.

**Operations On Arrays Data structure.**

**1.How To Acess?**
 **2. how to modify**


![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/oilzt55hm8eeh5ceaq2z.png)

So in the above image, we can look at each element of the array as stored at a specific index so we can Access that eleDelete element 3ment through the index.
_syntex: arrayname[index]_

**1 Acess**

```
console.log(numbers[0]) // 1
console.log(numbers[3]) // 4
```


The first element in the array has an index of 0, the second element has an index of 1, and so on.


**2 modify**
 
**Add Element** 

```
numbers[3] ="mydogname"
console.log(numbers) // [1,2,3,'mydogname' 5]
```
yes, we can store any data type in arrays also.


**Delete element**

```
 Delete numbers[3] 
console.log(numbers)  // [1,2,3, empty ,5] 

```
the very interesting thing to notice we try to delete the array element 
traditionally and we see "empty" at the undefined index.  
 resulted array also called spare array.

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/te93b0l0cokkcmjapyxu.png)

let's add again value at index 3.

```
numbers[3]=4
```

**Array properties  necessary to know**
Before we work on the array we need to know about the array property length 

```
console.log(numbers.length)  // 5
 
```

what if we need to access all elements, not just a single element?



**Iterating On Array**

```
for (let i =0 ; i<numbers.length ; i++ ) {
    console.log(numbers[i])     //  1,2,3,4,5    
}
```
so what  it will work like that 
 
first iteration. value of i =0    numbers[0] --> element at index 0  second iteration. value of i =1    numbers[1] --> element at index1  third  iteration. value of i =0    numbers[2] --> element at index2 fourth iteration. value of i =0    numbers[3] --> element at index3 fifth iteration. value of i =0    numbers[4] --> element at index 4 

so I <numbers. length condition is met loop will be stopped.


**Now we are ready to get the average of numbers in an array in an efficient way. **

```
let numbers = [1,2,3,4,5] 
let average=0;
let sum=0


for(let i=0 ;i<numbers.length ;i++)
{
    console.log(numbers[i])
    sum=sum +numbers[i]

}

  average = sum/numbers.length
   console.log(average)
```
**Benefits again to Remember**

 
now we can add how my numbers as we want without repeating ourselves  
which is the rule of programming DRY(DON'T REPEAT YOURSELF).

so guys that's, for now, stay tuned for the second episode about array methods.