数组拆分，多用于单个数组拆分多个数组，用处swiper里面

group(array, subGroupLength) {
      let index = 0;
      let newArray = [];
      while(index < array.length) {
          newArray.push(array.slice(index, index += subGroupLength));
      }
      return newArray;
    },

　　

that.group(array,6)