code: function each(obj, func, isArr) {
    if (!obj) {
      return;
    }
  
    if (isArr == null) {
      isArr = isArrayLike(obj);
    }
  
    if (isArr) {
      for (var i = 0, l = obj.length; i < l; i++) {
        var ret = func.call(obj, obj[i], i, l);
  
        if (ret === false) {
          break;
        }
      }
    } else {
      var keys = Object.keys(obj),
          _l = keys.length;
  
      for (var _i = 0; _i < _l; _i++) {
        var k = keys[_i],
            _ret = func.call(obj, obj[k], k, _i, _l);
  
        if (_ret === false) {
          break;
        }
      }
    }
  }
docs: 遍历数组或对象