Question

我有一个对象数组，并且正在使用es6寻找最有效的方法来根据material_id将它们分组

var data=[
  {material_id:1, item:'test'},
  {material_id:1,  item:'test2'},
  {material_id:2,  item:'test2'},
]

所以最后我想得到

var final_data = [
  1,2
 ]

THat是来自分组的material_id的ID

所以我已经尝试过了，但是在继续进行方面却陷入困境

let final_data = [];
data.forEach(item=>{
      //stuck here
})

我检查了This question ，但似乎没有显示分组

Answer 1

您可以ValueError Traceback (most recent call last) <ipython-input-72-7fee7a634922> in <module> ----> 1 da_autumn = xr.where(np.isin(da_temp.time.dt.month.values, autumn_mth_list), da_temp, 0) 2 da_autumn.values ~\anaconda3\envs\PlannedBurnWindow\lib\site-packages\xarray\core\computation.py in where(cond, x, y) 1115 join='exact', 1116 dataset_join='exact', -> 1117 dask='allowed') ~\anaconda3\envs\PlannedBurnWindow\lib\site-packages\xarray\core\computation.py in apply_ufunc(func, input_core_dims, output_core_dims, exclude_dims, vectorize, join, dataset_join, dataset_fill_value, keep_attrs, kwargs, dask, output_dtypes, output_sizes, *args) 967 join=join, 968 exclude_dims=exclude_dims, --> 969 keep_attrs=keep_attrs) 970 elif any(isinstance(a, Variable) for a in args): 971 return variables_vfunc(*args) ~\anaconda3\envs\PlannedBurnWindow\lib\site-packages\xarray\core\computation.py in apply_dataarray_vfunc(func, signature, join, exclude_dims, keep_attrs, *args) 216 217 data_vars = [getattr(a, 'variable', a) for a in args] --> 218 result_var = func(*data_vars) 219 220 if signature.num_outputs > 1: ~\anaconda3\envs\PlannedBurnWindow\lib\site-packages\xarray\core\computation.py in apply_variable_ufunc(func, signature, exclude_dims, dask, output_dtypes, output_sizes, keep_attrs, *args) 563 raise ValueError('unknown setting for dask array handling in ' 564 'apply_ufunc: {}'.format(dask)) --> 565 result_data = func(*input_data) 566 567 if signature.num_outputs == 1: ~\anaconda3\envs\PlannedBurnWindow\lib\site-packages\xarray\core\duck_array_ops.py in where(condition, x, y) 191 def where(condition, x, y): 192 """Three argument where() with better dtype promotion rules.""" --> 193 return _where(condition, *as_shared_dtype([x, y])) 194 195 ~\anaconda3\envs\PlannedBurnWindow\lib\site-packages\xarray\core\duck_array_ops.py in f(*args, **kwargs) 42 else: 43 wrapped = getattr(eager_module, name) ---> 44 return wrapped(*args, **kwargs) 45 else: 46 def f(*args, **kwargs): ValueError: operands could not be broadcast together with shapes (8760,) (8760,106,193) ()获取所有ID的数组，然后使用map()删除重复项

Set

Answer 2

借助unique函数，我能够像这样解决问题：

const unique = (value, index, self) => {
    return self.indexOf(value) === index
}


const data =[
  {material_id:1, item:'test'},
  {material_id:1,  item:'test2'},
  {material_id:2,  item:'test2'},
];

var final_data = [];

for(var i in data) {
    let row = data[i];
    final_data.push(row.material_id);
}
final_data = final_data.filter(unique);

console.log(final_data);

Answer 3

您可以使用reduce对数组进行分组，并使用Object.keys获取结果键。

var data=[
  {material_id:1, item:'test'},
  {material_id:1,  item:'test2'},
  {material_id:2,  item:'test2'},
]

let result = data.reduce((r, a) => {

  const {
    material_id,
    item
  } = a;

  r[a.material_id] = [...r[a.material_id] || [], {
    material_id,
    item
  }];

  return r;
}, {});


console.log(Object.keys(result));

Javascript通过带有对象数组的分组来获取最终键

3 个答案: