JavaScript Arrays

Definition: An array is an ordered list of values stored in one variable, written in square brackets [ ]. Positions (indexes) start at 0.

let fruits = ["apple", "banana", "cherry"];
console.log(fruits);
console.log(fruits[0]);     // apple
console.log(fruits.length); // 3

Example 1 — changing an item

fruits[1] = "blueberry";
console.log(fruits);

Example 2 — adding and removing

fruits.push("orange");    // add to end
fruits.unshift("mango");  // add to start
fruits.pop();             // remove last
fruits.shift();           // remove first
console.log(fruits);

Example 3 — looping

let nums = [10, 20, 30];
for (let n of nums) {
  console.log(n);
}

Example 4 — powerful array methods

let scores = [50, 80, 95, 30];
console.log(scores.includes(80));            // true
let passed = scores.filter(s => s >= 50);    // [50, 80, 95]
let doubled = scores.map(s => s * 2);        // [100, 160, 190, 60]
console.log(passed);
console.log(doubled);

💡 Tip: map (transform every item) and filter (keep some items) are used constantly in real JavaScript.