JavaScript Arrays

Arrays hold ordered lists of values. Everything in JavaScript has an array method waiting for it.

Creating and accessing

Use square brackets to create an array. Indexes start at 0.

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

Adding and removing

push adds to the end, pop removes the last item.

const stack = [];
stack.push("a");
stack.push("b");
console.log(stack);
stack.pop();
console.log(stack);

Looping

for...of walks each item in order.

const names = ["Ada", "Grace", "Linus"];
for (const name of names) {
  console.log("hi " + name);
}

Transforming with map and filter

map builds a new array, filter keeps only matching items.

const nums = [1, 2, 3, 4, 5];
const doubled = nums.map((n) => n * 2);
const evens = nums.filter((n) => n % 2 === 0);
console.log(doubled);
console.log(evens);