lodash pick in nested array

Question

I have an array of objects like this:

{
  "sizes":{
     "thumbnail":{
        "height":300,
        "width":300,
        "url":"http://example.com/wp-content/uploads/2017/04/web-300x300.jpg",
        "orientation":"landscape"
     },
     "medium":{
        "height":267,
        "width":400,
        "url":"http://example.com/wp-content/uploads/2017/04/web-400x267.jpg",
        "orientation":"landscape"
     },
     "large":{
        "height":441,
        "width":660,
        "url":"http://example.com/wp-content/uploads/2017/04/web-1024x684.jpg",
        "orientation":"landscape"
     },
     "full":{
        "url":"http://example.com/wp-content/uploads/2017/04/web.jpg",
        "height":1200,
        "width":1796,
        "orientation":"landscape"
     }
  },
  "mime":"image/jpeg",
  "type":"image",
  "subtype":"jpeg",
  "id":3589,
  "url":"http://example.com/wp-content/uploads/2017/04/web.jpg",
  "alt":"",
  "link":"http://example.com/web/",
  "caption":""
}

I'm using the following snippet to create a new array with just the alt, caption, id and url keys in the array:

images.map( ( image ) => pick( image, [ 'alt', 'caption', 'id', 'url' ] ) ),

My question is, how can I pick the sizes.thumbnail.url key instead of the root url key? Is it possible? If so, how?

Thanks in advance

Answer 1

Create an object with the url property and the value of sizes.thumbnail.url using _.get(), and combine it with to the results of the _.pick().

Note: I've used object spread to merge the results, but you can use Object.assign() or lodash's equivalent instead.

const images = [{"sizes":{"thumbnail":{"height":300,"width":300,"url":"http://example.com/wp-content/uploads/2017/04/web-300x300.jpg","orientation":"landscape"},"medium":{"height":267,"width":400,"url":"http://example.com/wp-content/uploads/2017/04/web-400x267.jpg","orientation":"landscape"},"large":{"height":441,"width":660,"url":"http://example.com/wp-content/uploads/2017/04/web-1024x684.jpg","orientation":"landscape"},"full":{"url":"http://example.com/wp-content/uploads/2017/04/web.jpg","height":1200,"width":1796,"orientation":"landscape"}},"mime":"image/jpeg","type":"image","subtype":"jpeg","id":3589,"url":"http://example.com/wp-content/uploads/2017/04/web.jpg","alt":"","link":"http://example.com/web/","caption":""}];

const result = images.map((image) => ({
  ..._.pick(image, ['alt', 'caption', 'id']),
  url: _.get(image, 'sizes.thumbnail.url')
}));

console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.10/lodash.min.js"></script>

A more generic solution would a function that accepts a list of paths, and generate an array of pairs [last part of path, value]. The function converts the pairs to an object using _.fromPairs() (or Object.fromEntries()):

const deepPick = (paths, obj) => 
  _.fromPairs(paths.map(p => [
    _.last(p.split('.')),
    _.get(obj, p),
  ]))

const images = [{"sizes":{"thumbnail":{"height":300,"width":300,"url":"http://example.com/wp-content/uploads/2017/04/web-300x300.jpg","orientation":"landscape"},"medium":{"height":267,"width":400,"url":"http://example.com/wp-content/uploads/2017/04/web-400x267.jpg","orientation":"landscape"},"large":{"height":441,"width":660,"url":"http://example.com/wp-content/uploads/2017/04/web-1024x684.jpg","orientation":"landscape"},"full":{"url":"http://example.com/wp-content/uploads/2017/04/web.jpg","height":1200,"width":1796,"orientation":"landscape"}},"mime":"image/jpeg","type":"image","subtype":"jpeg","id":3589,"url":"http://example.com/wp-content/uploads/2017/04/web.jpg","alt":"","link":"http://example.com/web/","caption":""}];

const result = images.map(image => deepPick(
  ['alt', 'caption', 'id', 'sizes.thumbnail.url'], 
  image
));

console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.10/lodash.min.js"></script>