使用Lodash展平嵌套的对象数组 [英] Flatten an nested array of objects using Lodash

问题描述

我的对象看起来像这样:

My object looks like this:

const features = [{
                  'name': 'feature1', 'tags':
                  [{'weight':10, 'tagName': 't1'},{'weight':20, 'tagName': 't2'}, {'weight':30, 'tagName': 't3'}]
                  },
                  {
                  'name': 'feature2', 'tags':
                  [{'weight':40, 'tagName': 't1'}, {'weight':5, 'tagName':'t2'}, {'weight':70, 'tagName':'t3'}]
                  },
                  {
                  'name': 'feature3', 'tags':[
                  {'weight':50, 'tagName': 't1'}, {'weight':2, 'tagName': 't2'}, {'weight':80, 'tagName': 't3'}]
                 }]

我希望我的输出看起来像这样:

I would like my output to look something like this:

const features = [{'name':'feature1', 'weight':10, 'tagName':'t1'}, 
                  {'name':'feature1', 'weight':20, 'tagName':'t2'}, ...
                  {'name':'feature3', 'weight':80, 'tagName':'t3'}]

我尝试了merge和flatten，但是它不起作用.

I tried to merge and the flatten but it does not work.

更新1 我试过了:

let feat = features;

results = []

_.each(feat, (item) => { 
                        console.log(item);
                        results.push(_.flatten(_.pick(item.tags, 'weight'))); // pick for certain keys. 
                       }

更新2 这解决了我的问题

_.each(features, (item) => { 
  _.each(item.tags, (itemTag) => { 
    results.push({'name':item.name, 'weight':itemTag.weight, 'tagName':itemTag.tagName})})})

但是我想知道是否还有更多的lodash方式！

But I want to know if there is a more lodash way to do this!

推荐答案

以下方法使用 flatMap 展平通过地图获取的tags.最后，使用 spread运算符来分配tag和feature名称中的值.

The approach below uses flatMap to flatten tags acquired through map. Finally, use the spread operator to assign the values from tag and the feature's name.

const result = _.flatMap(features, ({ name, tags }) =>
  _.map(tags, tag => ({ name, ...tag }))
);

const features = [{
    'name': 'feature1',
    'tags': [{
      'weight': 10,
      'tagName': 't1'
    }, {
      'weight': 20,
      'tagName': 't2'
    }, {
      'weight': 30,
      'tagName': 't3'
    }]
  },
  {
    'name': 'feature2',
    'tags': [{
      'weight': 40,
      'tagName': 't1'
    }, {
      'weight': 5,
      'tagName': 't2'
    }, {
      'weight': 70,
      'tagName': 't3'
    }]
  },
  {
    'name': 'feature3',
    'tags': [{
      'weight': 50,
      'tagName': 't1'
    }, {
      'weight': 2,
      'tagName': 't2'
    }, {
      'weight': 80,
      'tagName': 't3'
    }]
  }
];

const result = _.flatMap(features, ({ name, tags }) =>
  _.map(tags, tag => ({ name, ...tag }))
);

console.log(result);

.as-console-wrapper{min-height:100%;top:0}

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.js"></script>

这是使用 Array#reduce 和 Array#map 在 Array#concat 展平数组.

Here's a plain javascript solution that uses Array#reduce and Array#map with the help of Array#concat to flatten the array.

const result = features.reduce(
  (result, { name, tags }) => result
    .concat(tags.map(tag => ({ name, ...tag }))), 
  []
);

const features = [{
    'name': 'feature1',
    'tags': [{
      'weight': 10,
      'tagName': 't1'
    }, {
      'weight': 20,
      'tagName': 't2'
    }, {
      'weight': 30,
      'tagName': 't3'
    }]
  },
  {
    'name': 'feature2',
    'tags': [{
      'weight': 40,
      'tagName': 't1'
    }, {
      'weight': 5,
      'tagName': 't2'
    }, {
      'weight': 70,
      'tagName': 't3'
    }]
  },
  {
    'name': 'feature3',
    'tags': [{
      'weight': 50,
      'tagName': 't1'
    }, {
      'weight': 2,
      'tagName': 't2'
    }, {
      'weight': 80,
      'tagName': 't3'
    }]
  }
];

const result = features.reduce(
  (result, { name, tags }) => result
    .concat(tags.map(tag => ({ name, ...tag }))), 
  []
);

console.log(result);

.as-console-wrapper{min-height:100%;top:0}

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.js"></script>

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