javascript - 从不断变化的顺序的 JSON 响应中解析一个值

Question

我试图在 javscript 中解析来自我的家庭自动化系统的 JSON 响应。回复 可在此处获得

这只是响应的一小部分，而且，由于我不知道的原因，每次重新启动时键的顺序都会发生变化，su 使用数字索引不会真正起作用我需要能够存储 sensor.out 的状态值, sensor.in, sensor.door 到 andorid 上 tasker 的变量中我尝试使用 entity.id 进行选择，但由于某种原因代码从未完成（我相信我只是不知道我在做什么）

Answer 1

使用 ES6，您可以使用以下Array#find方法：

response.find(o => o.entity_id == 'sensor.out').state

见片段：

var response = [ { "attributes":{ "friendly_name":"door" }, "entity_id":"sensor.door", "last_changed":"2016-12-31T11:15:59.395808+00:00", "last_updated":"2016-12-31T11:15:59.395808+00:00", "state":"closed" }, { "attributes":{ "friendly_name":"In", "unit_of_measurement":"\u00b0C" }, "entity_id":"sensor.in", "last_changed":"2016-12-31T11:20:02.179821+00:00", "last_updated":"2016-12-31T11:20:02.179821+00:00", "state":"20.7" }, { "attributes":{ "changed_by":null, "code_format":".+", "friendly_name":"panel" }, "entity_id":"alarm_control_panel.panel", "last_changed":"2016-12-31T11:14:56.471966+00:00", "last_updated":"2016-12-31T11:14:56.471966+00:00", "state":"disarmed" }, { "attributes":{ "friendly_name":"Out", "unit_of_measurement":"\u00b0C" }, "entity_id":"sensor.out", "last_changed":"2016-12-31T11:14:58.452345+00:00", "last_updated":"2016-12-31T11:14:58.452345+00:00", "state":"7.1" }];
var state = response.find(o => o.entity_id == 'sensor.out').state;
console.log('sensor.out state is', state);

或者，您可以将响应转换为以实体 id 值作为键的对象，因此您可以像这样访问它response['session.out'].state：

response = Object.assign({}, ...response.map( o => ({[o.entity_id]: o}) ));

见片段：

var response = [ { "attributes":{ "friendly_name":"door" }, "entity_id":"sensor.door", "last_changed":"2016-12-31T11:15:59.395808+00:00", "last_updated":"2016-12-31T11:15:59.395808+00:00", "state":"closed" }, { "attributes":{ "friendly_name":"In", "unit_of_measurement":"\u00b0C" }, "entity_id":"sensor.in", "last_changed":"2016-12-31T11:20:02.179821+00:00", "last_updated":"2016-12-31T11:20:02.179821+00:00", "state":"20.7" }, { "attributes":{ "changed_by":null, "code_format":".+", "friendly_name":"panel" }, "entity_id":"alarm_control_panel.panel", "last_changed":"2016-12-31T11:14:56.471966+00:00", "last_updated":"2016-12-31T11:14:56.471966+00:00", "state":"disarmed" }, { "attributes":{ "friendly_name":"Out", "unit_of_measurement":"\u00b0C" }, "entity_id":"sensor.out", "last_changed":"2016-12-31T11:14:58.452345+00:00", "last_updated":"2016-12-31T11:14:58.452345+00:00", "state":"7.1" }];
response = Object.assign({}, ...response.map( o => ({[o.entity_id]: o}) ));
console.log('sensor.out state is', response['sensor.out'].state);

Answer 2

每个人都说的是正确的：响应中键的顺序无关紧要。使用（字符串）键，而不是数字索引。

var arr = [
  {
    "entity_id":"sensor.door",
    "state":"closed"
  }];   // other attributes chopped out for brevity

var entity_id_interested_in = 'sensor.door';
var state = '[entity_id not found in response]';
for (var i = 0; i < arr.length; i++) {

    console.log(arr[i].entity_id + ' state:' + arr[i].state);
    if (arr[i].entity_id == entity_id_interested_in)
    {
       state = arr[i].state;
       break;
    }
}
console.log (state);

Answer 3

如果您尝试使用索引从对象中选择属性，则不应该这样做，除非有非常具体的理由这样做。

幸运的是，这很好，您不需要知道顺序。我从您的 JSON 数组中取出两个对象，将属性打乱，并编写了一个函数，该函数返回包含您指定的键/值的任何对象。

你的问题有点难以理解，但我认为这会给你这个想法。

<script type="text/javascript">
let arr = [
  {
    "attributes":{
      "friendly_name":"door"
    },
    "entity_id":"sensor.frontdoor",
    "last_changed":"2016-12-31T11:15:59.395808+00:00",
    "last_updated":"2016-12-31T11:15:59.395808+00:00",
    "state":"closed"
  },
  {
    "last_changed":"2016-12-31T11:15:59.395808+00:00",
    "state":"closed",
    "attributes":{
      "friendly_name":"door"
    },
    "entity_id":"sensor.backdoor",
    "last_updated":"2016-12-31T11:15:59.395808+00:00"
  }
];

function findKey ( theKey, theVal ) {
  let reduced = arr.filter ( d => {
    return d [ theKey ] === theVal;
  });

  return reduced;
}

let targets = findKey ( 'entity_id', 'sensor.backdoor' );
targets.forEach ( d => {
   // This check is a little naive, but should give you the idea
   if ( 'state' in d ) {
      console.log ( d.state );
   }
} );
</script>