javascript - 提醒数组内的数据细节

Question

我遇到了 javascript 初学者的问题。我将这些数据存储在一个数组中，我试图提醒数据以查看它是否已 check out 。

我想提醒自己 all 的平均距离，而不是 both 行星，尽管在这种情况下两者都是，但我最终想要一个数组保留的不仅仅是两个。现在，它只是提醒数组列表中最后一条记录的距离，这很奇怪。我认为这将是所有人的平均水平。

此外，我如何对数组中“距离”属性的最小和最大数字进行编程，然后用它来提醒“主机名”。因此，如果我有一个按钮并单击“Closest”，“Distance [pc]” 中编号最小的主机名将被提醒。我只需要一个“距离”的代码示例，这样我就知道如何对所有其他变量执行相同的操作。

如果您愿意帮忙，谢谢!

顺便说一句，列表是 JSON 数据。提及这一点可能很重要。

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<pre class="snippet-code-js lang-js prettyprint-override"><code>    // this array holds the json data, in this case stastics of exoplanets retrieved from nasa's website   
    var arr=        [ {
   "rowid": 684,
   "Host name": "K2-15",
   "Number of Planets in System": 1,
   "Planet Mass or M*sin(i)[Jupiter mass]": null,
   "Planet Radius [Jupiter radii]": 0.221,
   "Planet Density [g": {
      "cm**3]": null
   },
   "Distance [pc]": 437,
   "Effective Temperature [K]": 5131,
   "Date of Last Update": "7/16/2015"
},
 {
   "rowid": 687,
   "Host name": "K2-17",
   "Number of Planets in System": 1,
   "Planet Mass or M*sin(i)[Jupiter mass]": null,
   "Planet Radius [Jupiter radii]": 0.199,
   "Planet Density [g": {
      "cm**3]": null
   },
   "Distance [pc]": 134,
   "Effective Temperature [K]": 4320,
   "Date of Last Update": "7/16/2015"
}];

    //every record is put in a variable		
    var rowid;	
    var hostName;
    var numberOfPlanetsInSystem;
    var planetMass;
    var planetRadius;
    var distance;
    var effectiveTemperature;

    for(var i=0;i<arr.length;i++){

       rowid= arr[i]["rowid"];
       hostName= arr[i]["Host name"];
       numberOfPlanetsInSystem= arr[i]["Number of Planets in System"];
       planetMass= arr[i]["Planet Mass or M*sin(i)[Jupiter mass]"];
       planetRadius= arr[i]["Planet Radius [Jupiter radii]"];
       distance= arr[i]["Distance [pc]"];
       effectiveTemperature= arr[i]["Effective Temperature [K]"];
    };

    //alert to test it out
    alert(distance);</code></pre>
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Answer 1

let totalDistance = maxDistance = 0;
let minDistance = arr[0]["Distance [pc]"];
let closestHost = farthestHost = "";
for(let i = 0; i < arr.length; i ++) {
    totalDistance += arr[i]["Distance [pc]"]
    if (arr[i]["Distance [pc]"] < minDistance) {
        minDistance = arr[i]["Distance [pc]"];
        closestHost = arr[i]["Host name"];
    }
    if (arr[i]["Distance [pc]"] > maxDistance) {
        maxDistance = arr[i]["Distance [pc]"];
        farthestHost = arr[i]["Host name"];
    }
}
let meanDistance = totalDistance/arr.length;