获取数组中出现最多的元素

1、方法一：需要三次循环，缺点：大量的循环操作会消耗大量的计算资源、代码多

      const arr = ['a', 'c', 'b', '1', '9', 'b', 'sdf', '6', 'b', 'aaaa', '汉字', '汉字', 'sdf', '-', '-']
      const obj = {}
      arr.forEach(item => {
        if (obj[item]) {
          obj[item]++
        } else {
          obj[item] = 1
        }
      })


      const numArr = []
      for (const item in obj) {
        numArr.push(obj[item])
      }
      const sortNum = numArr.sort((a, b) => {
        return b - a
      })



      for (const item in obj) {
        if (obj[item] === sortNum[0]) {
          console.log('出现最多的元素和次数', item, obj[item])
        }
      }

2、一次循环，使用二维数组处理元素集合

      const arr = ['a', 'a', 'c', 'b', '1', '9', 'b', 'sdf', '6', 'b', 'aaaa', '汉字', '汉字', 'sdf', '-', '-']
      const obj = {}
      const newArr = []
      let d = 0
      let dStr = ''
      arr.forEach(item => {
        if (obj[item] === undefined) {
          newArr.push([])
          const index = newArr.length - 1
          obj[item] = index
        }
        newArr[obj[item]].push(item)
        const newItem = newArr[obj[item]]
        if (newItem.length > d) {
          d = newItem.length
          dStr = newItem[0]
        }
      })
      console.log('新数组', newArr)
      console.log('出现最多的元素和次数:', dStr, d)