在包含复杂嵌套数组的 javascript 对象中查找项目答案

【问题标题】：Finding items in a javascript object consisting of complex nested arrays在包含复杂嵌套数组的 javascript 对象中查找项目
【发布时间】：2018-05-08 14:17:04
【问题描述】：

我需要在各种数组中的 javascript 对象中查找项目。数组位于嵌套的 javascript 对象中。我已经实现了一种获取所需数据的方法，但它似乎很长，有 4 个嵌套的 for 循环。

我意识到我可以使用 for 循环来遍历元素，但这不是最漂亮的方式。我已经研究了如何使用过滤器功能来访问我感兴趣的顶级项目，但努力研究如何过滤内部项目。

在我下面的代码中，interesting_lines 得到了适当的填充。下一阶段是创建一个包含 measure.value.label 为“fw”的所有元素的列表，然后打印 measure.value.value 数字。我该怎么做？

// lines crossed that we are interested in
let interest = ["Entry", "Exit"];

let lines = {"element":[{"element-id":2,"element-name":"line_2.1","sensor-type":"MULTI_SENSOR","data-type":"LINE","from":"2018-05-08T08:59:00Z","to":"2018-05-08T09:00:00Z","resolution":"ONE_MINUTE","measurement":[{"from":"2018-05-08T08:59:00Z","to":"2018-05-08T09:00:00Z","value":[{"value":0,"label":"fw"},{"value":0,"label":"bw"}]}]},{"element-id":3,"element-name":"line_2.2","sensor-type":"MULTI_SENSOR","data-type":"LINE","from":"2018-05-08T08:59:00Z","to":"2018-05-08T09:00:00Z","resolution":"ONE_MINUTE","measurement":[{"from":"2018-05-08T08:59:00Z","to":"2018-05-08T09:00:00Z","value":[{"value":1,"label":"fw"},{"value":0,"label":"bw"}]}]},{"element-id":1,"element-name":"Entry","sensor-type":"MULTI_SENSOR","data-type":"LINE","from":"2018-05-08T08:59:00Z","to":"2018-05-08T09:00:00Z","resolution":"ONE_MINUTE","measurement":[{"from":"2018-05-08T08:59:00Z","to":"2018-05-08T09:00:00Z","value":[{"value":1,"label":"fw"},{"value":0,"label":"bw"}]}]},{"element-id":0,"element-name":"Exit","sensor-type":"MULTI_SENSOR","data-type":"LINE","from":"2018-05-08T08:59:00Z","to":"2018-05-08T09:00:00Z","resolution":"ONE_MINUTE","measurement":[{"from":"2018-05-08T08:59:00Z","to":"2018-05-08T09:00:00Z","value":[{"value":0,"label":"fw"},{"value":0,"label":"bw"}]}]},{"element-id":4,"element-name":"line_2.3","sensor-type":"MULTI_SENSOR","data-type":"LINE","from":"2018-05-08T08:59:00Z","to":"2018-05-08T09:00:00Z","resolution":"ONE_MINUTE","measurement":[{"from":"2018-05-08T08:59:00Z","to":"2018-05-08T09:00:00Z","value":[{"value":0,"label":"fw"},{"value":0,"label":"bw"}]}]},{"element-id":5,"element-name":"line_2.4","sensor-type":"MULTI_SENSOR","data-type":"LINE","from":"2018-05-08T08:59:00Z","to":"2018-05-08T09:00:00Z","resolution":"ONE_MINUTE","measurement":[{"from":"2018-05-08T08:59:00Z","to":"2018-05-08T09:00:00Z","value":[{"value":0,"label":"fw"},{"value":0,"label":"bw"}]}]}]};


console.log(`lines in collection=${lines.element.length}`);  // 6

// filter function on line name
function required_line(item) {
    for(var i = 0; i < interest.length; ++i) {
        if (item["element-name"] == interest[i]) {
            return true;
    }
    }
    return false;
}

const interesting_lines = lines.element.filter(required_line);
console.log(`result of filter: ${JSON.stringify(interesting_lines)} `);

// filter out by label - eg fwd???
var morefiltered=interesting_lines.filter( function(element) { return element["measurement"]["value"]["label"] == "fw"; });
// above line fails - TypeError: Cannot read property 'label' of undefined

console.log(`2nd level filter: ${JSON.stringify(morefiltered)} `);

我的预期输出是：

forward line crossing numbers:
line name: Entry, value: 1
line name: Exit, value: 0

【问题讨论】：

预期的输出究竟是什么？
measurement 和 value 是数组。

标签： javascript arrays node.js filter

【解决方案1】：

由于measurement 和value 是数组，因此您必须遍历它们，

const morefiltered=interesting_lines.filter( element => { 
    return element.measurement.filter(a => {
        return a.value.filter(b => {
            return b.label == "fw";
        })
    })
});

并创建一个空数组并用匹配的值填充它：

// lines crossed that we are interested in
let interest = ["Entry", "Exit"];

let lines = {
  "element": [{
    "element-id": 2,
    "element-name": "line_2.1",
    "sensor-type": "MULTI_SENSOR",
    "data-type": "LINE",
    "from": "2018-05-08T08:59:00Z",
    "to": "2018-05-08T09:00:00Z",
    "resolution": "ONE_MINUTE",
    "measurement": [{
      "from": "2018-05-08T08:59:00Z",
      "to": "2018-05-08T09:00:00Z",
      "value": [{
        "value": 0,
        "label": "fw"
      }, {
        "value": 0,
        "label": "bw"
      }]
    }]
  }, {
    "element-id": 3,
    "element-name": "line_2.2",
    "sensor-type": "MULTI_SENSOR",
    "data-type": "LINE",
    "from": "2018-05-08T08:59:00Z",
    "to": "2018-05-08T09:00:00Z",
    "resolution": "ONE_MINUTE",
    "measurement": [{
      "from": "2018-05-08T08:59:00Z",
      "to": "2018-05-08T09:00:00Z",
      "value": [{
        "value": 1,
        "label": "fw"
      }, {
        "value": 0,
        "label": "bw"
      }]
    }]
  }, {
    "element-id": 1,
    "element-name": "Entry",
    "sensor-type": "MULTI_SENSOR",
    "data-type": "LINE",
    "from": "2018-05-08T08:59:00Z",
    "to": "2018-05-08T09:00:00Z",
    "resolution": "ONE_MINUTE",
    "measurement": [{
      "from": "2018-05-08T08:59:00Z",
      "to": "2018-05-08T09:00:00Z",
      "value": [{
        "value": 1,
        "label": "fw"
      }, {
        "value": 0,
        "label": "bw"
      }]
    }]
  }, {
    "element-id": 0,
    "element-name": "Exit",
    "sensor-type": "MULTI_SENSOR",
    "data-type": "LINE",
    "from": "2018-05-08T08:59:00Z",
    "to": "2018-05-08T09:00:00Z",
    "resolution": "ONE_MINUTE",
    "measurement": [{
      "from": "2018-05-08T08:59:00Z",
      "to": "2018-05-08T09:00:00Z",
      "value": [{
        "value": 0,
        "label": "fw"
      }, {
        "value": 0,
        "label": "bw"
      }]
    }]
  }, {
    "element-id": 4,
    "element-name": "line_2.3",
    "sensor-type": "MULTI_SENSOR",
    "data-type": "LINE",
    "from": "2018-05-08T08:59:00Z",
    "to": "2018-05-08T09:00:00Z",
    "resolution": "ONE_MINUTE",
    "measurement": [{
      "from": "2018-05-08T08:59:00Z",
      "to": "2018-05-08T09:00:00Z",
      "value": [{
        "value": 0,
        "label": "fw"
      }, {
        "value": 0,
        "label": "bw"
      }]
    }]
  }, {
    "element-id": 5,
    "element-name": "line_2.4",
    "sensor-type": "MULTI_SENSOR",
    "data-type": "LINE",
    "from": "2018-05-08T08:59:00Z",
    "to": "2018-05-08T09:00:00Z",
    "resolution": "ONE_MINUTE",
    "measurement": [{
      "from": "2018-05-08T08:59:00Z",
      "to": "2018-05-08T09:00:00Z",
      "value": [{
        "value": 0,
        "label": "fw"
      }, {
        "value": 0,
        "label": "bw"
      }]
    }]
  }]
};


// console.log(`lines in collection=${lines.element.length}`);  // 6

// filter function on line name
function required_line(item) {
  for (var i = 0; i < interest.length; ++i) {
    if (item["element-name"] == interest[i]) {
      return true;
    }
  }
  return false;
}

const interesting_lines = lines.element.filter(required_line);
//console.log(`result of filter: ${JSON.stringify(interesting_lines)} `);
let values = [];
// filter out by label - eg fwd >>>
const morefiltered = interesting_lines.filter(element => {
  return element.measurement.filter(a => {
    return a.value.filter(b => {
      if(b.label == "fw"){
        values.push({name : element["element-name"], value : b.value});
        return true;
      }
    })
  })
});

console.log('values : ', JSON.stringify(values))
console.log(`2nd level filter: ${JSON.stringify(morefiltered)} `);

【讨论】：

【解决方案2】：

数据结构不是很好，所以如果你可以改变它，我会推荐它，这反过来会使你的算法更简单。

我已尝试使用 underscoreJS 为您解决问题，但我不完全确定这是您想要的。

var myObjects = _.filter(lines.element, function(l){
  return _.any(interest, function(i){
    return l["element-name"] == i;
  });
});

【讨论】：