An array is a common data structure that holds items of the same type, in TypeScript, unlike other languages, an array doesn't have a fixed length. Also, in TypeScript, you don't have to re-organize all elements of an array when makings operations like insert or delete.

### Representation

![array](https://res.cloudinary.com/dje4crtui/image/upload/v1622593241/array-img_kn9hp3.png)

* **Elements** are the items stored in an array
* **Index** is the location of an element in an array, it goes from 0 to (array length - 1)


```typescript
/** An array can be written like this **/

const numbers: number[] = [1, 2, 3, 4]
const names = string[] = ['Snake', 'Ocelot', 'Otacon', 'Naomi']

/** Also can be written using a generic array type, Array<elemType> **/

let list: Array<number> = [1, 2, 3, 4]
let list: Array<string> = ['Snake', 'Ocelot', 'Otacon', 'Naomi']
```

### Basics operations

**Traverse** - Print all array items one by one

```typescript
/** 3 ways to iterate an array **/

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

for(const item of array) {
    console.log(item)
}

array.forEach(item => {
    console.log(item)
})
```

**Insertion** - Add an item

```typescript
/** add to the end **/
array.push(5)

/** add to the beginning **/
array.unshift(0)

/** add in a specific index position **/
array.splice(3, 0, 8) // add 8 in the index 3
```

**Deletion** - Remove an item

```typescript
/** remove from the end **/
array.pop()

/** remove from the beginning **/
array.shift()

/** remove from a specific index position **/
array.splice(2, 1) // remove from index 2
```

**Update** - Update an item

```typescript
/** update element in position 1 **/
array[1] = 7
```

**Search** - Search by an item

```typescript
/** you can traverse an array to find an element by its value, or simply use the .find() function **/

const item = array.find(item => item === 3) // search by an item with value 3
```

### Strings are arrays of characters

All above operations can be performed on strings to solve problems like count the occurrences of a character in a string:

```typescript
let str = "aabbccdd"
let occurrences = 0

for(let i=0; i < str.length; i++) {
    if(str[i] === "c") {
        occurrences++
    }
}

console.log(occurrences) // prints 2
```

An array is a common data structure that holds items of the same type, in TypeScript, unlike other languages, an array doesn't have a fixed length.

Ricardo Borges

Data Structures in TypeScript - Array