How to find the elements that occur in an array the maximum number of times?

Question

JavaScript

Please tell me.
I write in TypeScript.
There is an array of the form
[1,1,1,1,1, 3,3,3,3,3, 5,5 ,6,6,6, 7,7,7,7,7]
Get it is necessary
[1,3,7]
These are the elements that occur the maximum number of times.
Yes, I know how to solve this problem stupidly in the forehead, heaping up intermediate arrays and cycles.
But any beautiful and and effective decision interests. Like, for example, in sql or linq, something like group by, count, max, etc.

Answer 1

const arr = [1,1,1,1,1, 3,3,3,3,3, 5,5 ,6,6,6, 7,7,7,7,7];

const map = {};
arr.forEach(el => map[el] = map[el] ? map[el] + 1 : 1);
const max = Math.max(...Object.values(map));
const result = Object.keys(map).filter(key => map[key] === max);

console.log(result); // [1 ,3, 7]

Answer 2

Option with lodash:

const arr = [1,1,1,1,1, 3,3,3,3,3, 5,5 ,6,6,6, 7,7,7,7,7]
const items = _.countBy(arr) // {1: 5, 3: 5, 5: 2, 6: 3, 7: 5}
const max = _.max(_.toArray(items)) // 5
const result = []
_.forIn(items, (value, key) => {
  if (value === max) result.push(key)
})

Answer 3

[1,1,1,1,1, 3,3,3,3,3, 5,5 ,6,6,6, 7,7,7,7,7].filter((v, i, a) => a.indexOf(v) === i);