js 数组拆分

    split_array(arr, len) {
      var a_len = arr.length;
      var result = [];
      for (var i = 0; i < a_len; i += len) {
        result.push(arr.slice(i, i + len));
      }
      return result;
    },

 可以使用简单方法，引入 lodash

_.chunk(['a', 'b', 'c', 'd'], 2);
// => [['a', 'b'], ['c', 'd']]
 
_.chunk(['a', 'b', 'c', 'd'], 3);
// => [['a', 'b', 'c'], ['d']]