Create a new result from an existing array

Question

If I have a sample data that looks like this I need to get finalResult array from result array:

let result = [{
    type: ['Science'],
    link: "www.educatorsector.com"
  },
  {
    type: ['Sports', 'News'],
    link: "www.skysports-news.com"
  },
  {
    type: ['Sports', 'Science'],
    link: "www.cnn-news.com"
  }];

finalResult = [
{ type : "Science", numberOfLinks : 2 }, 
{ type : "Sports", numberOfLinks : 2 },
{ type : "News", numberOfLinks : 1 }]

orThisFinalResult = [
{ type : "Science", links : ["www.educatorsector.com", "www.cnn-news.com"],
{ type : "Sports", links : ["www.skysports-news.com", "www.cnn-news.com"],
{ type : "News", links : ["www.skysports-news.com"]
 }

You can use `Array#reduce` to accumulate the counts in an object as iterate through the array. Then transform that object into the array you want via `Object#keys` or similar — Andrew Li, Nov 26 '20 at 23:13

score 2 · Answer 1 · answered Nov 26 '20 at 23:14

You can use Array.reduce to create an object which counts all the links for each type; then use Object.entries to get those values as an array, finally using Array.map to convert to an array of objects:

let result = [{
    type: ['Science', 'Business'],
    link: "www.educatorsector.com"
  },
  {
    type: ['Sports', 'News'],
    link: "www.skysports-news.com"
  },
  {
    type: ['Sports', 'Health', 'Science'],
    link: "www.cnn-news.com"
  },
  {
    type: ['Health'],
    link: "www.healthsector.com"
  }
];

let output = Object.entries(result
    .reduce((c, o) => {
      o.type
        .forEach(t => c[t] = (c[t] || 0) + 1);
      return c;
    }, {}))
  .map(([type, numberOfLinks]) => ({
    type,
    numberOfLinks
  }));

console.log(output);

score 2 · Answer 2 · answered Nov 27 '20 at 00:17

Use Array.flatMap() to get an array of types. Reduce the array of types to a Map of counts. Convert the Map to an array of entries, and then map it to an array of objects:

const result = [{"type":["Science","Business"],"link":"www.educatorsector.com"},{"type":["Sports","News"],"link":"www.skysports-news.com"},{"type":["Sports","Health","Science"],"link":"www.cnn-news.com"},{"type":["Health"],"link":"www.healthsector.com"}];

const counts = Array.from(
    result
      .flatMap(o => o.type) // flatten to array of types
      .reduce((acc, type) => // create a Map of counts
        acc.set(type, (acc.get(type) || 0) + 1), 
      new Map)
  )
  .map(([type, numberOfLinks]) => ({ type, numberOfLinks })); // convert the Map's entries to an array of objects

console.log(counts);

Create a new result from an existing array

2 Answers2