Question

目前我正在编写一个从Police.UK数据库中提取的程序，以下是从API请求时数据的解释方式。数据传递到循环中并存储值，如下所示。我认为问题出在var outcome = data[i]["outcome_status"];之间。问题是结果状态可以是null还是包含两个字符串outcome_status.date和outcome_status.category，我如何区分和确定天气值为null或包含更多信息。

谢谢！

function create_marker(lat, lng, cat, time, id, street, outcome) {
completed_requests = 1;
document.getElementById("popular_crime").innerText = "";
document.getElementById("num_of_crimes").innerText = "";
var current_lat_lng = [];
current_lat_lng.push(lat, lng, cat, time, id, street, outcome);
chunksize = 7;
var chunks = [];
current_lat_lng.forEach((item) => {
    if (!chunks.length || chunks[chunks.length - 1].length == chunksize)
        chunks.push([]);
    chunks[chunks.length - 1].push(item);
});
for (var z = 0; z < chunks.length; z++) {
    var a = chunks[z];
    var icons = L.icon({
        iconSize: [32, 32],
        iconUrl: 'asset/images/' + a[2] + '.png'
    });
}
switch (a[2]) {
    case 'antisocialbehaviour':
        var popup2 = "<center><br><h2>Anti Social Behaviour</h2><img src=\"asset/images/antisocialbehaviour.png\"height=\"42\" width=\"42\"><h3>Crime Identity Number:</h3><p>" + id + "</p><h3>Month:</h3><p>" + time + "</p><h3>Street Name:</h3><p>" + street + "</p><h2><h3>Outcome:</h3><p>" + outcome + "</p><h2></center>";
        var marker = L.marker(new L.LatLng(a[0], a[1]), {
            icon: icons,
            time: a[3],
            id: a[4],
            street: a[5],
            outcome: a[6]
        });
        marker.addTo(group1).bindPopup(popup2);
        asbcount++
        break;
        break;
    default:
        break;
}

     function get_JSON(url, callback_func) {
       var xmlhttp = new XMLHttpRequest();
       xmlhttp.onreadystatechange = function() {
         var check1 = xmlhttp.readyState == 4 && this.status == 200;
         var check2 = check1 && typeof callback_func === "function";
         if (check2) {
           json_obj = JSON.parse(this.responseText);
           callback_func(json_obj);
         }

       }
       console.log("Getting stats for", url)
       xmlhttp.open("POST", url, true);
       xmlhttp.send();
     }

     function mode(c) {
       var popular_str = "";
       var popular_num = 0;

       for (item in c) {
         num = c[item]
         if (num > popular_num) {
           popular_str = item;
           popular_num = num;
         }
       }

       return popular_str;
     }

     function JSON_callback(data) {
       completed_requests++;
       var data_len = data.length;
       if (data[0] != undefined) {
         for (var i = 0; i < data_len; i++) {
           cat1 = data[i]["category"];
           cat = cat1.replace(/-/g, "");
           cat3 = cat1.replace(/-/g, " ");
           id = data[i]["persistent_id"];
           lat = data[i]["location"]["latitude"];
           lng = data[i]["location"]["longitude"];
           street = data[i]["location"]["street"]["name"];
           time = data[i]["month"];
           var outcome = data[i]["outcome_status"];
           if (cat3 in crimes) {
             crimes[cat3]++;
           } else {
             crimes[cat3] = 1;
           }
           drawChart();
           console.log(data)
           committed = true;
           create_marker(lat, lng, cat, time, id, street, outcome);
           num_of_crimes++;
         }
       }
       document.getElementById("num_of_crimes").innerText = num_of_crimes;
       if (completed_requests == 1) {
         console.log("Requests done");

         //console.log(crimes);
         if (committed) {
           document.getElementById("popular_crime").innerText = mode(crimes);
         } else {
           document.getElementById("popular_crime").innerText = "None";

         }
       }
     }

以下是来自API的JSON外观

[
   {
      "category":"anti-social-behaviour",
      "location_type":"Force",
      "location":{
         "latitude":"53.746850",
         "street":{
            "id":1289421,
            "name":"On or near Denshaw Drive"
         },
         "longitude":"-1.589005"
      },
      "context":"",
      "outcome_status":null,
      "persistent_id":"a42e1e83ed8055156c1cae319a38b590957de163e8eaeb7884c2b7dd1491056d",
      "id":55436628,
      "location_subtype":"",
      "month":"2017-03"
   },
   {
      "category":"burglary",
      "location_type":"Force",
      "location":{
         "latitude":"53.746074",
         "street":{
            "id":1289411,
            "name":"On or near Hull Street"
         },
         "longitude":"-1.596109"
      },
      "context":"",
      "outcome_status":{
         "category":"Unable to prosecute suspect",
         "date":"2017-03"
      },
      "persistent_id":"906849d248a5b0b26857184a291cbd1e952dfbe62783ad59fdad1c58737386ec",
      "id":55411246,
      "location_subtype":"",
      "month":"2017-03"
   }
]

Answer 1

如果提供的Object.assign为outcome，您可以使用null将var data = [{ "category": "anti-social-behaviour", "location_type": "Force", "location": { "latitude": "53.746850", "street": { "id": 1289421, "name": "On or near Denshaw Drive" }, "longitude": "-1.589005" }, "context": "", "outcome_status": null, "persistent_id": "a42e1e83ed8055156c1cae319a38b590957de163e8eaeb7884c2b7dd1491056d", "id": 55436628, "location_subtype": "", "month": "2017-03" }, { "category": "burglary", "location_type": "Force", "location": { "latitude": "53.746074", "street": { "id": 1289411, "name": "On or near Hull Street" }, "longitude": "-1.596109" }, "context": "", "outcome_status": { "category": "Unable to prosecute suspect", "date": "2017-03" }, "persistent_id": "906849d248a5b0b26857184a291cbd1e952dfbe62783ad59fdad1c58737386ec", "id": 55411246, "location_subtype": "", "month": "2017-03" } ]; for (var i = 0; i < 2; i++) { var outcome = Object.assign({ category: "", date: "" }, data[i]["outcome_status"]); console.log(outcome); }设置为某些默认值。

outcome = outcome.date + ":" + outcome.category;

如果您希望结果只是一个字符串，您可以使用

<input type="text" name="mail" id="mail">

或其他取决于你的欲望。

显示为[object Object]的JSON循环

1 个答案: