如何过滤本机反应中的对象数组？

Question

我想将此数据数组过滤为州和城市数组。我如何使用 lodash 或任何其他更好的方法而不是 for 循环和维护额外的数组来实现这一点。

 data: [
    { id: 1, name: Mike, city: philps, state: New York},
    { id: 2, name: Steve, city: Square, state: Chicago},
    { id: 3, name: Jhon, city: market, state: New York},
    { id: 4, name: philps, city: booket, state: Texas},
    { id: 5, name: smith, city: brookfield, state: Florida},
    { id: 6, name: Broom, city: old street, state: Florida},
]

哪个用户点击 state ，出现状态列表。

 {state: New York, count: 2},
{state: Texas, count: 1},
{state: Florida, count: 2},
{state: Chicago, count: 1},

当用户单击特定状态时，会出现该状态的 cities 列表。对于前。当用户点击纽约州时，

 {id:1, name: Mike, city: philps}
{id:3, name: Jhon, city: market}

原文由 Balasubramanian 发布，翻译遵循 CC BY-SA 4.0 许可协议

Answer 1

使用 lodash，您可以将 _.filter 与对象一起使用 --- [`.matches`](https://lodash.com/docs/#matches) iteratee shorthand_ for filtering the object with a given key/value pair and

使用 _.countBy 和 _.map 获取状态计数。

 var data = [{ id: 1, name: 'Mike', city: 'philps', state: 'New York' }, { id: 2, name: 'Steve', city: 'Square', state: 'Chicago' }, { id: 3, name: 'Jhon', city: 'market', state: 'New York' }, { id: 4, name: 'philps', city: 'booket', state: 'Texas' }, { id: 5, name: 'smith', city: 'brookfield', state: 'Florida' }, { id: 6, name: 'Broom', city: 'old street', state: 'Florida' }];

console.log(_.filter(data, { state: 'New York' }));
console.log(_
    .chain(data)
    .countBy('state')
    .map((count, state) => ({ state, count }))
    .value()
);

 .as-console-wrapper { max-height: 100% !important; top: 0; }

 <script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.15.0/lodash.min.js"></script>

原文由 Nina Scholz 发布，翻译遵循 CC BY-SA 4.0 许可协议

Answer 2

您可以使用 native javascript 通过应用 filter 方法来执行此操作，该方法接受 callback 提供的函数作为 _参数_。

 let data = [ { id: 1, name: 'Mike', city: 'philps', state:'New York'}, { id: 2, name: 'Steve', city: 'Square', state: 'Chicago'}, { id: 3, name: 'Jhon', city: 'market', state: 'New York'}, { id: 4, name: 'philps', city: 'booket', state: 'Texas'}, { id: 5, name: 'smith', city: 'brookfield', state: 'Florida'}, { id: 6, name: 'Broom', city: 'old street', state: 'Florida'}, ]

data = data.filter(function(item){
   return item.state == 'New York';
}).map(function({id, name, city}){
    return {id, name, city};
});
console.log(data);

另一种方法是使用 arrow 函数。

 let data = [ { id: 1, name: 'Mike', city: 'philps', state:'New York'}, { id: 2, name: 'Steve', city: 'Square', state: 'Chicago'}, { id: 3, name: 'Jhon', city: 'market', state: 'New York'}, { id: 4, name: 'philps', city: 'booket', state: 'Texas'}, { id: 5, name: 'smith', city: 'brookfield', state: 'Florida'}, { id: 6, name: 'Broom', city: 'old street', state: 'Florida'}, ]

data = data.filter((item) => item.state == 'New York').map(({id, name, city}) => ({id, name, city}));
console.log(data);

原文由 Mihai Alexandru-Ionut 发布，翻译遵循 CC BY-SA 4.0 许可协议