const searchIn = (string, haystack) => {
    const result = []
    const matches = []
    const values = string.replace(/[^\wа-яё\s]/gi, '')

    haystack.forEach((item) => {
      let matchesCount = 0

      values.split(' ').forEach((needle) => {
        if (needle && item.tags.includes(needle)) {
          matchesCount += 1
        }
      })

      if (matchesCount) {
        matches.push(matchesCount)
        result.push({ matchesCount, item })
      }
    })

    const maxMatchedValue = Math.max(...matches)
    return result.filter(({ matchesCount }) => matchesCount === maxMatchedValue)
  }

const arr1 = [
  {id: 1, tags: 'some, value,  values,  empty...'},
  {id: 2, tags: 'some, value'},
  {id: 3, tags: 'some'},
  {id: 4, tags: ''},
]
const arr2 = [
  {id: 1, tags: 'some, values,  empty'},
  {id: 2, tags: 'empty, value'},
  {id: 3, tags: 'value'},
  {id: 4},
]

const searchString = 'some values  searching not including...'
const filterByTags = (arr) => arr.filter(({ tags }) => tags && tags.length)
const haystack = [arr1, arr2].map(filterByTags).reduce((a, b) => a.concat(b))

searchIn(searchString, haystack)

/*
[
  {
    "matchesCount": 2,
    "item": {
      "id": 1,
      "tags": "some, value,  values,  empty..."
    }
  },
  {
    "matchesCount": 2,
    "item": {
      "id": 1,
      "tags": "some, value,  values,  empty"
    }
  }
]
*/