Array in JavaScript
📚 What is an Array?
An Array in JavaScript is a special variable that holds a list of values. These values can be of any type — numbers, strings, objects, even other arrays! Arrays are ordered and indexed, starting at 0.
>>“Arrays turn scattered data into structured sequences.” 🧠
📦 Creating an Array
Basic Array Creation
let fruits = ["🍎", "🍌", "🍇"];
let numbers = [1, 2, 3, 4, 5];
let mixed = [42, "hello", true, null];Note
💡 You can store any data type — even functions or objects — in an array.
🔢 Accessing Array Elements
Use square brackets with the index to access elements.
Access Elements
let fruits = ["apple", "banana", "cherry"];
console.log(fruits[0]); // "apple"
console.log(fruits[2]); // "cherry"Note
📌 Array indices start at 0, not 1.
✏️ Modifying Elements
Change Array Elements
let colors = ["red", "blue"];
colors[1] = "green";
console.log(colors); // ["red", "green"]➕ Common Array Methods
- push() – Add to end
- pop() – Remove from end
- shift() – Remove from start
- unshift() – Add to start
- length – Get number of elements
Using Array Methods
let items = [1, 2];
items.push(3); // [1, 2, 3]
items.pop(); // [1, 2]
items.unshift(0); // [0, 1, 2]
items.shift(); // [1, 2]🔁 Looping Through Arrays
for Loop
let names = ["John", "Jane", "Joe"];
for (let i = 0; i < names.length; i++) {
console.log(names[i]);
}forEach Method
names.forEach(function(name) {
console.log(name);
});Note
💡 forEach is a cleaner way to loop, especially for readability.
📐 Useful Array Methods
- map() – Transform each item
- filter() – Return items that match a condition
- find() – Return the first match
- includes() – Check if item exists
- sort() – Sort items
Example: filter and map
let scores = [40, 80, 95, 60];
let passed = scores.filter(score => score > 60);
let doubled = scores.map(score => score * 2);🧪 Checking Arrays
Use Array.isArray() to confirm if a value is an array.
Check if it's an Array
console.log(Array.isArray([1, 2, 3])); // true
console.log(Array.isArray("hello")); // false📚 Summary Table
| Operation | Method | Description |
|---|---|---|
| Add at end | push() | Adds one or more items |
| Remove from end | pop() | Removes the last item |
| Add at start | unshift() | Adds to the front |
| Remove from start | shift() | Removes the first item |
| Loop | forEach() | Runs a function for each item |
🌐 Useful Resources
>>“Arrays are not just lists — they’re the foundation of structured, powerful data manipulation in JavaScript.” 🔧