javascript - How to group an array of objects by key? - Stack Overflow

admin管理员组

文章数量:1317898

How do you group an array of objects by an object key to create a new array of objects based on the grouping? For example, I have an array of car objects:

const array = [
  {red: [ {height: 50} ]},
  {green: [ {height: 20} ]},
  {blue: [ {height: 30} ]},
  {blue: [ {height: 40} ]},
  {red: [ {height: 10} ]},
  {green: [ {height: 60} ]}
]

I want to create a new array of objects.(key is color)

const result = [
  {red: [{height: 50}, {height: 10}]},
  {green: [{height: 20}, {height: 60}]},
  {blue: [{height: 30}, {height: 40}]}
]

I tried to use lodash.groupBy, however I don't know how to solve this problem at all.

How do you group an array of objects by an object key to create a new array of objects based on the grouping? For example, I have an array of car objects:

const array = [
  {red: [ {height: 50} ]},
  {green: [ {height: 20} ]},
  {blue: [ {height: 30} ]},
  {blue: [ {height: 40} ]},
  {red: [ {height: 10} ]},
  {green: [ {height: 60} ]}
]

I want to create a new array of objects.(key is color)

const result = [
  {red: [{height: 50}, {height: 10}]},
  {green: [{height: 20}, {height: 60}]},
  {blue: [{height: 30}, {height: 40}]}
]

I tried to use lodash.groupBy, however I don't know how to solve this problem at all.

• javascript
• logic
• lodash

Share Improve this question Follow edited Sep 12, 2020 at 4:53 sonicmario asked Jan 14, 2019 at 8:06 sonicmariosonicmario 61199 silver badges2323 bronze badges 5

• The first one is exactly doing what OP was asking suing lodash – mplungjan Commented Jan 14, 2019 at 8:12
• @mplungjan all dupes seem to be grouping by key value, not key name. – Keith Commented Jan 14, 2019 at 8:13
• Hey, It's not duplicate question. Look at my question carefully. – sonicmario Commented Jan 14, 2019 at 8:15
• Im on mobile atm, but the trick would be to use Object.keys(item)[0] to get keyname for grouping purposes. – Keith Commented Jan 14, 2019 at 8:18
• 1 stackoverflow./a/40774906/295783 - seems very close to the accepted answer – mplungjan Commented Jan 14, 2019 at 8:26

Add a ment  | 

2 Answers 2

Sorted by: Reset to default 6

Using array reduce you can iterate data and calculate result object.

const array = [
  { 'red': [ { height: 50 } ] },
  { 'green': [ { height: 20 } ] },
  { 'blue': [ { height: 30 } ] },
  { 'blue': [ { height: 40 } ] },
  { 'red': [ { height: 10 } ] },
  { 'green': [ { height: 60 } ] }
];

const res = array.reduce((acc, element) => {
  // Extract key and height value array
  const [key, heightValue] = Object.entries(element)[0];
  // Get or create if non-exist, and push height value from array, index 0
  (acc[key] || (acc[key] = [])).push(heightValue[0]);
  return acc;
}, {});

console.log(res);

You can use lodash's _.mergeWith() to bine the objects with the same key, and then use _.map() to convert it back to an array:

const array = [{"red":[{"height":50}]},{"green":[{"height":20}]},{"blue":[{"height":30}]},{"blue":[{"height":40}]},{"red":[{"height":10}]},{"green":[{"height":60}]}]

const fn = _.flow([
  arr => _.mergeWith({}, ...arr, (o, s) => _.isArray(o) ? o.concat(s) : s),
  objs => _.map(objs, (v, k) => ({ [k]: v }))
])

const result = fn(array)

console.log(result)

<script src="https://cdnjs.cloudflare./ajax/libs/lodash.js/4.17.11/lodash.min.js"></script>

本文标签： javascriptHow to group an array of objects by keyStack Overflow