resolveDeps.js

function resolveDeps (pkgs, name) {
  const resolved = [];
  const missingRequired = [];
  const missingOptional = [];

  const queue = [name];

  while (queue.length) {
    const curr = queue.shift();
    const pkg = pkgs[curr];

    if (!pkg) {
      missingRequired.push(pkg);
      continue;
    }

    const deps = pkg.dependencies || {};

    for (let dep in deps) {
      const depOpts = deps[dep];
      const necessity = depOpts.type;

      if (!pkgs[dep]) {
        if (necessity === 'optional') missingOptional.push(dep);
        else missingRequired.push(dep);

        continue;
      }

      queue.push(dep);
    }

    resolved.push(curr);
  }

  return {
    resolved: [...new Set(resolved.reverse())],
    missingRequired: [...new Set(missingRequired)],
    missingOptional: [...new Set(missingOptional)],
  };
}

const pkgs = {
  'accord': {
    dependencies: {
      'dot-prop': { type: 'required' },
      'filenamify': { type: 'required' },
      'got': { type: 'optional' },
      'write-file-atomic': { type: 'required' },
      'example-package': { type: 'optional' },
    },
  },

  'dot-prop': {
    dependencies: {
      'is-obj': { type: 'required' },
    },
  },
  'filenamify': {
    dependencies: {
      'example-package': { type: 'required' },
    },
  },

  'is-obj': {
    dependencies: {},
  },
  'example-package': {
    dependencies: {
      'is-obj': { type: 'required' },
      'non-existant-package': { type: 'required' },
    },
  },
};

const ret = resolveDeps(pkgs, 'accord');
console.log(ret);