用逗号和最大计数器合并数组元素

const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11];

const mergeArray = (arr, size) => {
  let res = [];
  for (i = 0; i < arr.length; i += size) { 
    res.push(arr.slice(i, i + size).join(','));
  }
  return res;
}

console.log(mergeArray(arr, 3));

const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11];
var i, j, newArr=[], size = 3;
for (i=0,j=arr.length; i<j; i+=size) {
  newArr.push(arr.slice(i, i+size).join());
}
console.log(newArr);

const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11];

function mergeArray(arr, n) {
    return arr
          .reduce((all, el, i) => {

              const ind = Math.floor(i/n);
              all[ind] = [...all[ind] || [], el]

              return all;

          },[])
          .map(a => a.join(','))
}

console.log(mergeArray(arr, 3));

var data = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11],
    result = data.join(',').match(/\d+(,\d+(,\d+)?)?/g)

console.log(result);