arr.reduce((a,b)=>(a.arr[b] = a.arr[b] || [], a.arr[b][a.arr[b].length-(a.last === b ? 1 : 0)] = [...(a.arr[b][a.arr[b].length-(a.last === b ? 1 : 0)]||[]), b], a.last = b, a), {last: -1, arr: []}).arr.slice(1)

只遍歷一次數(shù)組
如果當(dāng)前數(shù)等于上一個(gè)，則結(jié)果數(shù)組的最后一個(gè)子數(shù)組更新，否則則對(duì)應(yīng)數(shù)組項(xiàng)添加新數(shù)組。要求數(shù)字必須是大于-1的整數(shù)才行。

// 拋個(gè)磚.
var arr = [1, 1, 2, 2, 2, 1, 1, 3, 3, 1];

var map = {};
var result = [];

arr.forEach((el, ind) => {
  if (map[el]) {
    if (ind - map[el].ind > 1) {
      map[el].ind = ind;
      map[el].value.push([el]);
    } else {
      map[el].value[map[el].value.length - 1].push(el);
      map[el].ind += 1;
    }
  } else {
    map[el] = {
      value: [[el]],
      ind
    }
  }
})

for (let k in map) {
  result.push(map[k].value)
}

// result就是要的結(jié)果

var arr=[1,1,2,2,2,1,1,3,3,1];
m = new Map();
i = 0;
for(var j=1;j<arr.length;j++){
    if(arr[j] != arr[i]){
        if(m.has(arr[i])){
            m.get(arr[i]).push(arr.slice(i, j));
        }else{
            m.set(arr[i], [arr.slice(i, j)]);
        }
        i = j;
    }
}   //一次循環(huán)復(fù)雜度O(n)
if(m.has(arr[i])){
    m.get(arr[i]).push(arr.slice(i));
}else{
    m.set(arr[i], [arr.slice(i)]);
}
res = [];
m.forEach((o)=>{
    if(o.length == 1){
        res.push(o[0])
    }else{
        res.push(o)
    }
})    //一次循環(huán)復(fù)雜度O(m) m遠(yuǎn)小于n所以最終復(fù)雜度O(n)