Get count from Array of arrays

Question

I have an array of arrays below. With ES6, how can I get a count of each value Good, Excellent & Wow into a new array e.g [{name: Good, count: 4} {name: Excellent, count: 5}, {name:Wow, count:2}] in dynamic style. I am attempting to use Object.assign but I am failing to "unique" out the count of the key plus instead, I need to use an array as I am trying to render this out on the front end. Do I need to use reduce? how?

let k = 0
const stats = {}
const remarks = [
  [{name: "Good"}],
  [{name: "Good"}, {name: "Excellent"}],
  [{name: "Good"}, {name: "Excellent"}, {name: "Wow"}],
  [{name: "Good"}, {name: "Excellent"}, {name: "Wow"}],
  [{name: "Excellent"}],
  [{name: "Excellent"}]
]

remarks.forEach((arr) => {
  arr.map((e) => {
    Object.assign(stats, { [e.name]: k = k + 1 })
  })
})

console.log(stats);

Output:

stats: {Good: 8, Excellent: 11, Wow: 9}

Which is Incorrect plus I need to use an array.

Expected output:

[{name: Good, count: 4} {name: Excellent, count: 5}, {name:Wow, count:2}]

Answer 1

Flatten the array of arrays and reduce it starting with an object like : { Good: 0, Excellent: 0, Wow: 0}

then .map the Object.entries of the result to transform it to an array :

const remarks = [
  [{ name: "Good" }],
  [{ name: "Good" }, { name: "Excellent" }],
  [{ name: "Good" }, { name: "Excellent" }, { name: "Wow" }],
  [{ name: "Good" }, { name: "Excellent" }, { name: "Wow" }],
  [{ name: "Excellent" }],
  [{ name: "Excellent" }]
];

const result = Object.entries(
  remarks.flat().reduce(
    (all, { name }) => {
      all[name] += 1;
      return all;
    },
    { Good: 0, Excellent: 0, Wow: 0 }
  )
).map(([name, count]) => ({ name, count }));

console.log(result);

Answer 2

You can try below logic:

var data = [[{name: "Good"}],[{name: "Good"}, {name:"Excellent"}],[{name: "Good"}, {name:"Excellent"}, {name:"Wow"}],[{name: "Good"}, {name:"Excellent"}, {name:"Wow"}],[{name:"Excellent"}],[{name:"Excellent"}]]

var nData = [];

(data || []).forEach( e => {
  (e || []).forEach(ei => {
    var i = (index = nData.findIndex(d => d.name === ei.name)) >=0 ? index : nData.length;
    nData[i] = {
      name: ei.name,
      count : (nData[i] && nData[i].count ? nData[i].count : 0)+1
    }
  });
});

console.log(nData);

Hope this helps!

Answer 3

You can use reduce, then convert the result into an array of objects:

const counts = remarks.reduce((result, list) => {
  list.forEach(remark => {
    result[remark.name] = (result[remark.name] || 0) + 1;
  });
}, {});
const finalResult = [];
for (let name in counts) {
  finalResult.push({name, count: counts[name]});
}