Paths and file URLs

// The extension of the last part of a POSIX path: "todo.txt" -> ".txt".
export function extname(p) {
  return p.slice(p.indexOf("."));
}

console.log(extname("/home/ada/notes/todo.txt"));

import {test} from 'node:test';
import assert from 'node:assert/strict';
import {extname} from './main.js';

const check = (p, want) => assert.equal(extname(p), want, `extname(${JSON.stringify(p)}) returned ${JSON.stringify(extname(p))}, expected ${JSON.stringify(want)}`);

test('a plain file name', () => {
  check('todo.txt', '.txt');
  check('/home/ada/notes/todo.txt', '.txt');
});

test('only the last dot counts', () => {
  check('archive.tar.gz', '.gz');
});

test('a dot in a folder name does not count', () => {
  check('/home/ada/v1.2/notes', '');
});

test('no extension: no dot, or only a leading dot', () => {
  check('README', '');
  check('/home/ada/.env', '');
});

test('a trailing dot is an extension of its own', () => {
  check('index.', '.');
});

{
  "type": "module"
}

// Joins POSIX path parts and tidies the result, like path.posix.join.
export function joinPosix(...parts) {
  return parts.join("/");
}

console.log(joinPosix("docs", "..", "notes.txt"));

import {test} from 'node:test';
import assert from 'node:assert/strict';
import {joinPosix} from './main.js';

const check = (parts, want) => {
  const got = joinPosix(...parts);
  assert.equal(got, want, `joinPosix(${parts.map((p) => JSON.stringify(p)).join(', ')}) returned ${JSON.stringify(got)}, expected ${JSON.stringify(want)}`);
};

test('parts are joined with /', () => {
  check(['/home/ada', 'notes', 'todo.txt'], '/home/ada/notes/todo.txt');
});

test('.. removes the part before it', () => {
  check(['docs', '..', 'notes.txt'], 'notes.txt');
  check(['/home/ada/shop/src', '..', 'data', 'prices.json'], '/home/ada/shop/data/prices.json');
});

test('several slashes and . parts are tidied', () => {
  check(['a//', 'b'], 'a/b');
  check(['./a', './b'], 'a/b');
});

test('a leading slash on a later part is glued on', () => {
  check(['/srv/uploads', '/etc/passwd'], '/srv/uploads/etc/passwd');
});

test('.. at the start of a relative path stays, at the root it stops', () => {
  check(['..', 'a'], '../a');
  check(['/', '..', 'etc'], '/etc');
});

test('nothing left gives .', () => {
  check([], '.');
  check(['a', '..'], '.');
});

test('a part that is not a string throws a TypeError', () => {
  assert.throws(() => joinPosix('notes', 2026), TypeError, 'joinPosix("notes", 2026) should throw a TypeError');
});

{
  "type": "module"
}

import path from "node:path";
import {readFileSync} from "node:fs";

export function here(name) {
  return name;
}

export function hereUrl(name) {
  return new URL(name);
}

export function readHere(name) {
  return readFileSync(name, "utf8");
}

import {test} from 'node:test';
import assert from 'node:assert/strict';
import {here, hereUrl, readHere} from './main.js';

test('here() is the file inside the folder of main.js', () => {
  const got = here('notes.txt');
  const folder = import.meta.dirname;
  assert.ok(got.startsWith(folder) && got.endsWith('notes.txt') && got.length === folder.length + 'notes.txt'.length + 1, `here('notes.txt') returned ${JSON.stringify(got)}; expected notes.txt inside ${folder}`);
});

test('hereUrl() is a file: URL next to main.js', () => {
  const got = hereUrl('notes.txt');
  assert.ok(got instanceof URL, 'hereUrl() should return a URL object');
  assert.equal(got.href, new URL('./notes.txt', import.meta.url).href, `hereUrl('notes.txt') returned ${got.href}`);
});

test('readHere() reads the text of notes.txt', () => {
  assert.equal(readHere('notes.txt'), 'buy tea\ncall Ben\n', `readHere('notes.txt') returned ${JSON.stringify(readHere('notes.txt'))}`);
});

buy tea
call Ben

{
  "type": "module"
}