lodash 在嵌套数组中选择

Question

我有一个像这样的对象数组：

{
  "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":""
}

我使用以下代码片段创建一个新数组，其中仅包含数组中的alt、caption和键：idurl

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

我的问题是，如何选择sizes.thumbnail.url密钥而不是根url密钥？是否可以？如果是这样，怎么办？

提前致谢

Answer 1

sizes.thumbnail.url使用url 属性和 using 的值创建一个对象_.get()，并将其与_.pick().

注意：我使用object spread来合并结果，但您可以使用Object.assign()or lodash 的等效项代替。

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>

更通用的解决方案是一个接受路径列表的函数，并生成一个数组对[路径的最后一部分，值]。_.fromPairs()该函数使用(或)将对转换为对象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>