Answer 1

// 隨機生成 Array
function randomArray(length = 10, max = 100) {
  return Array.from({ length }, () => ~~(Math.random() * max))
}

// 10位分組
function newArray(array) {
  return array
    .reduce((acc, c) => {
      let i = ~~(c / 10)
      if (!acc[i]) acc[i] = []
      acc[i].push(c)
      return acc
    }, [])
    .filter(c => !!c)
    .map(arr => Array.from(new Set(arr)).sort())
}

// 連續數列分組
function continueArray(array) {
  return Array.from(new Set(array))
    .sort((a, b) => a - b)
    .reduce(
      (acc, c, i, arr) => {
        if (i === 0) acc[0].push(c)
        else {
          if (arr[i - 1] !== c - 1) acc.push([])
          acc[acc.length - 1].push(c)
        }
        return acc
      },
      [[]]
    )
}

let a = randomArray(10, 20)
newArray(a)
continueArray(a)