# Array Methods You Must Know (JavaScript)

When you start JavaScript, arrays look very simple.  
But after some time you realize most real work happens **inside arrays** — looping, transforming data, filtering values, calculating totals.

And instead of writing long loops every time, JavaScript gives built-in array methods which make life much easier.

Let’s go through the important ones every beginner should know.

* * *

## push() and pop() → add / remove from end

Think of push and pop like a stack.

### push()

Adds item at the end.

Example:

Before → `[10, 20, 30]`  
After push(40) → `[10, 20, 30, 40]`

Useful when you want to keep adding new data.

* * *

### pop()

Removes last item.

Before → `[10, 20, 30]`  
After pop() → `[10, 20]`

Pop also returns the removed value.

* * *

## shift() and unshift() → start of array

These are similar, but work at the beginning.

### unshift()

Adds item at start.

Before → `[20, 30]`  
After unshift(10) → `[10, 20, 30]`

* * *

### shift()

Removes first item.

Before → `[10, 20, 30]`  
After shift() → `[20, 30]`

* * *

## forEach() → simple iteration

forEach is used when you just want to run something for each item.

Example idea:  
Print each number in array.

It does not return a new array.  
It is mainly for side effects like logging or updating UI.

So if you need transformation, forEach is not the best choice.

* * *

## map() → transform each element

map creates a **new array** by changing each item.

Example:  
Numbers → `[2, 4, 6]`  
Double them using map → `[4, 8, 12]`

### Why not use a for loop?

You can use a loop, but map is cleaner and shorter.  
It also avoids manually pushing values into a new array.

Think of map as:  
“Take each value → change it → return new array”

* * *

## filter() → select specific values

filter is used when you only want some items.

Example:  
Numbers → `[5, 12, 8, 20]`  
Filter numbers > 10 → `[12, 20]`

filter does not change original array.  
It creates a new array with matching values.

So map = change values  
filter = select values

* * *

## reduce() → combine values into one result

reduce feels confusing at first, but idea is simple.

reduce takes many values and turns them into **one final value**.

Example:  
Find sum of `[10, 20, 30]`

Result → `60`

reduce keeps an accumulator which stores the running result.

You don’t need to master reduce now, just remember:  
reduce = accumulate / combine

* * *

## Small comparison (loop vs map/filter)

Traditional loop:

*   more lines
    
*   manual array handling
    
*   easy to make mistakes
    

map / filter:

*   shorter
    
*   readable
    
*   intention is clear
    

That’s why modern JS prefers array methods.