# Array Methods You Must Know

Think of an array as a toolbox. In our last post, we learned how to look inside the box. Now, we’re learning how to add, remove, and transform the tools inside without breaking a sweat.

Following are the topics that we are going to cover in this blog...

*   push() and pop()
    
*   shift() and unshift()
    
*   map()
    
*   filter()
    
*   reduce() (basic explanation only)
    
*   forEach()
    

* * *

## Adding & Removing (The Fast Track)

These methods allow you to quickly change the contents of your array.

*   `push()` **/** `pop()`**:** Work at the **end** of the array.
    
*   `unshift()` **/** `shift()`**:** Work at the **beginning** of the array.
    

```plaintext
let stack = ["Book1", "Book2"];

stack.push("Book3"); // ["Book1", "Book2", "Book3"] - Add to end
stack.pop();         // ["Book1", "Book2"] - Remove from end

stack.unshift("Newspaper"); // ["Newspaper", "Book1", "Book2"] - Add to start
stack.shift();              // ["Book1", "Book2"] - Remove from start
```

* * *

## Transformation Methods: `map()`, `filter()`, & `forEach(), reduce()`

These are the heavy hitters. They allow you to process every item in an array in one go.

#### `forEach()` **— The Elegant Loop**

Instead of writing a complex `for` loop, `forEach` simply performs an action for every item. it will **return the output on same array that was earlier.**

```plaintext
let users = ["Alice", "Bob", "Charlie"];
users.forEach(name => console.log("User: " + name));
```

#### `map()` **— The Transformer**

`map()` creates a **new array** by performing an operation on every element. It doesn’t change the original; it gives you a modified copy.

```plaintext
let prices = [10, 20, 30];
let discountedPrices = prices.map(p => p * 0.9); 

console.log(discountedPrices); // [9, 18, 27]
```

#### `filter()` **— The Security Guard**

`filter()` creates a **new array** containing only the items that pass a specific "test."

```plaintext
let ages = [12, 25, 17, 30];
let adults = ages.filter(age => age >= 18);

console.log(adults); // [25, 30]
```

### `reduce()` **— The Accumulator**

`reduce()` is used when you want to take an entire array and "squash" it into a **single value** (like a total sum).

Think of it like a snowball rolling down a hill it keeps gathering more until it reaches the bottom.

```plaintext
let bills = [50, 100, 25];
let total = bills.reduce((accumulator, current) => accumulator + current, 0);

console.log(total); // 175
```

* * *

## Conclusion

Using methods like `map()` and `filter()` is a milestone in your journey. It marks the transition from writing code that simply "works" to writing code that is **functional, clean, and professional**.