pick-deeper

A utility function. Like Lodash.pick, it picks properties form objects. In addition to that, it picks properties beyond level 1 (e.g. profile.name) and inside arrays (e.g. posts.*.title).

Useful for offline storage of big objects (e.g. api call response) in order to save memory.

Unlike other similar Lodash.pick augmentations, this one is compatible with es6 modules and picks from arrays.

Install

npm i pick-deeper

Usage

Let's suppose you want to add offline storage to your web app. You want to show on the main screen the titles of the post of the currently logged in user, and while you're at it, some information about the user.

You've got in memory a profile object that contains all of the posts, and all of the posts are composed by a title and a body.

You won't need to display the body in your page.

import { pickDeeper } from 'pick-deeper';

const profile = {
  id: '12345',
  profile: {
    name: 'Dom',
    surname: 'Plumitallo',
  },
  posts: [
    {
      title: 'Title 1',
      body: '...a very long body...',
    },
    {
      title: 'Title 2',
      body: '...a very long body...',
    }
  ],
};

const skimmedProfile = pickDeeper(profile, ['id', 'profile.name', 'posts.*.title']);
// returns {
//   id: '12345', 
//   profile: {name: 'Dom'},
//   posts: [{title: 'Title1'}, {title: 'Title2'}]
// }

// ...later on, you can
localStorage.set('profile', skimmedProfile);

You've saved all of the memory space that you would've taken by storying the bodies that you won't even show on the page.

In addition to that, the next time the browser looks for some app's storage to evict from the cache, there's less chance it's gonna be yours.

Contributing

PRs accepted.

Good-To-Knows

No in-place editing.

Picking happens by returning a new object that only has the picked properties, as in Lodash.pick.

Arrays keep their original structure.

All of the fields have the same index in both the original and result array. To achieve this, fields that don't match have to occupy some space in the array, so they're just replaced with undefined.

License

MIT © Domenico Plumitallo