immutableTransitiveDependencies.js

const test = require('tape');

function resolver(deps) {
  function directDeps(className) {
    return deps[className] || [];
  }

  function transitiveDeps(className) {
    return directDeps(className).reduce((set, className) => {
      [className, ...transitiveDeps(className)].forEach((v) => set.add(v));
      return set;
    }, new Set());
  }

  function resolve(className) {
    return [...transitiveDeps(className)].sort();
  }

  return { resolve };
}

test('resolves dependencies for any given class', (assert) => {
  deps = resolver({
    A: ['B', 'C'],
    B: ['C', 'E'],
    C: ['G'],
    D: ['A', 'F'],
    E: ['F'],
    F: ['H']
  });

  assert.deepEqual(deps.resolve('A'), ['B', 'C', 'E', 'F', 'G', 'H']);
  assert.deepEqual(deps.resolve('B'), ['C', 'E', 'F', 'G', 'H']);
  assert.deepEqual(deps.resolve('C'), ['G']);
  assert.deepEqual(deps.resolve('D'), ['A', 'B', 'C', 'E', 'F', 'G', 'H']);
  assert.deepEqual(deps.resolve('E'), ['F', 'H']);
  assert.deepEqual(deps.resolve('F'), ['H']);
  assert.end();
});