Algorithms

Most algorithmic work uses methods on arrays and other built-in collections.

Sorting

const xs = [5, 1, 4, 2, 3];
xs.sort((a, b) => a - b);              // ascending
xs.sort((a, b) => b - a);              // descending

people.sort((a, b) => a.age - b.age);

Search

Linear search.

const i = xs.indexOf(target);
const found = xs.find((x) => x.name === "operator");

Binary search on a sorted array.

function binarySearch(xs: number[], target: number): number {
    let lo = 0, hi = xs.length;
    while (lo < hi) {
        const mid = (lo + hi) >>> 1;
        if (xs[mid] === target) return mid;
        if (xs[mid] < target)   lo = mid + 1;
        else                    hi = mid;
    }
    return -1;
}

Map / Filter / Reduce

const total = xs
    .filter((x) => x > 0)
    .map((x) => x * x)
    .reduce((acc, x) => acc + x, 0);

Recursion

function fact(n: number): number {
    return n <= 1 ? 1 : n * fact(n - 1);
}

Async

Coordinate concurrent work with Promise.all and async / await:

async function fetchAll(urls: string[]): Promise<string[]> {
    const responses = await Promise.all(urls.map((u) => fetch(u)));
    return Promise.all(responses.map((r) => r.text()));
}