將不同函數的參數發送到 function

Question

    function layerQuery(objectId) {
    const featureLayer = view.map.layers.getItemAt(0);
    const queryParams = featureLayer.createQuery();
   

    queryParams.where = "objectid=" + objectId;
    queryParams.outFields = ["x", "y", "z"];

    featureLayer.queryFeatures(queryParams).then(function (results) {
      const coords = results.features[0].attributes;
      direction_lookup(Promise, Promise,coords.x,coords.y)
    });
    const objectIdNext = objectId + 1
    const queryParamsTb = featureLayer.createQuery();
    queryParamsTb.where = "objectid=" + objectIdNext;
    queryParamsTb.outFields = ["x", "y", "z"];
    featureLayer.queryFeatures(queryParamsTb).then(function (results) {
      var coordstb = results.features[0].attributes;
      direction_lookup(coordstb.x, coordstb.y,Promise,Promise)
    });
    //console.log(coordstb.x)
    
  }

我想把我們上面兩個函數的結果得到的四個參數發送給下面的function。

function direction_lookup(destination_x, origin_x, destination_y, origin_y) {
    var compass_brackets, compass_lookup, degrees_final, degrees_temp, deltaX, deltaY;
    deltaX = destination_x - origin_x;
    deltaY = destination_y - origin_y;
    degrees_temp = Math.atan2(deltaX, deltaY) / Math.PI * 180;
    

    if (degrees_temp < 0) {
      degrees_final = 360 + degrees_temp;
    } else {
      degrees_final = degrees_temp;
    }

    compass_brackets = ["N", "NE", "E", "SE", "S", "SW", "W", "NW", "N"];
    compass_lookup = Math.round(degrees_final / 45);
    return [compass_brackets[compass_lookup], degrees_final];
  }

  console.log(direction_lookup(destination_x, origin_x, destination_y, origin_y));

'direction lookup' function 有四個參數。 我想從不同的函數中兩個兩個地發送這四個參數。 我可以這樣做嗎

Answer 1

您嘗試執行的操作是不可能的，因為您的direction_lookup function 需要這四個參數作為數字坐標，它不希望看到任何Promise對象或解析它們。 執行此操作的標准方法是等到知道所有值后再調用 function，如下所示：

function layerQuery(objectId) {
    const featureLayer = view.map.layers.getItemAt(0);
    const queryParams = featureLayer.createQuery();
   

    queryParams.where = "objectid=" + objectId;
    queryParams.outFields = ["x", "y", "z"];

    featureLayer.queryFeatures(queryParams).then((results) => {
      const feature1Coords = results.features[0].attributes;
      const objectIdNext = objectId + 1
      const queryParamsTb = featureLayer.createQuery();
      queryParamsTb.where = "objectid=" + objectIdNext;
      queryParamsTb.outFields = ["x", "y", "z"];
      featureLayer.queryFeatures(queryParamsTb).then((secondResults) => {
         const feature2Coords = secondResults.features[0].attributes;
         direction_lookup(feature2Coords.x, features2Coords.y,feature1Coords.x,feature1Coords.y);
      });
    }); 
   }

現在，您執行第一個查詢並在執行第二個查詢時保留 scope 中的結果，最后在准備好 go 的兩組坐標時調用direction_lookup 。

箭頭函數的行為類似於常規函數，但保留父函數 scope，這可以避免很多混亂，因此對於此類任務，它是一種稍微方便一些的表示法。