从 JSON 响应中解析一个不断改变顺序的值

Question

我正在尝试用 javscript 解析来自我的家庭自动化系统的 JSON 响应。回应是 available here

这只是响应的一小部分，另外，由于我不知道的原因，每次重新启动时键的顺序都会改变，使用数字索引的 su 不会真正起作用我需要能够将 sensor.out、sensor.in、sensor.door 的状态值存储到 andorid 上的 tasker 变量中我尝试 select 使用 entity.id，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

如果您尝试对对象的 select 属性使用索引，则不应该这样做，除非有非常具体的原因。

幸运的是没关系，你不需要知道顺序。我从你的 JSON 数组中取出了两个对象，打乱了属性，并编写了一个函数 returns 任何包含你指定的 key/val 的对象。

你的问题有点难以理解，但我想这会给你思路。

<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>

Answer 2

大家都说的对：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

在 ES6 中你可以使用 Array#find 方法：

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

查看片段：

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，这样您就可以像 response['session.out'].state:

一样访问它

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

查看片段：

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);

从 JSON 响应中解析一个不断改变顺序的值

Parsing a value from JSON response that keeps changing order

javascript

json

tasker