JavaScript中通过对象配置FeatureLayer标签不显示问题排查

我需要为多个FeatureLayer添加标签，因此创建了包含图层配置的对象数组：

const layersByYears = [ 
    { year: 1918, layers: [ 
        { layerID: "1", opacity: 1.0, name: "name1", featureLayer: null, labelingInfo: labelClass },
        { layerID: "2", opacity: 1.0, name: "name2", featureLayer: null },
        { layerID: "3", opacity: 1.0, name: "name3", featureLayer: null },
        { layerID: "4", opacity: 1.0, name: "name4", featureLayer: null }
    ] },
    // 其他年份图层配置...
]

预先定义的标签配置变量：

const labelClass = {
    symbol: {
        type: "text",  // autocasts as new TextSymbol()
        color: "black",
        font: {  // autocast as new Font()
          family: "Playfair Display",
          size: 12,
          weight: "bold"
        }
      },
      labelPlacement: "above-center",
      labelExpressionInfo: {
        expression: "42"        
      }
}

创建FeatureLayer的函数：

const createFL = (layer) => {
        if(layer.featureLayer !== null && layer.featureLayer !== undefined)
            return;
        layer.featureLayer = new FeatureLayer({ 
            portalItem: {
                id: layer.layerID,
                opacity: layer.opacity !== undefined ? layer.opacity : 1.0,
                visible: false,
            }, 
            labelingInfo: layer.labelingInfo 
     })
}

目前能正常加载ArcGIS Online上的点图层，但看不到标签，labelClass已在layersByYears之前声明，请问问题出在哪里？

• labelingInfo格式错误：ArcGIS API for JavaScript中，labelingInfo要求是LabelClass对象数组，而非单个对象。需要将labelingInfo的值改为数组形式，比如：

  { layerID: "1", opacity: 1.0, name: "name1", featureLayer: null, labelingInfo: [labelClass] },
  

• FeatureLayer参数层级错误：opacity和visible是FeatureLayer的顶层属性，不属于portalItem对象，需要调整初始化代码的参数位置：

  layer.featureLayer = new FeatureLayer({ 
      portalItem: {
          id: layer.layerID,
      },
      opacity: layer.opacity !== undefined ? layer.opacity : 1.0,
      visible: false,
      labelingInfo: layer.labelingInfo 
  })
  

• 字体兼容性问题：Playfair Display是自定义字体，若当前环境未加载该字体，可能导致标签显示异常。可以先替换为系统默认字体（如Arial）测试，确认是否是字体原因。

• 图层可见性检查：代码中设置了visible: false，需确保后续有将图层设为可见（比如调用layer.featureLayer.visible = true），否则标签会随图层一起隐藏。

内容的提问来源于stack exchange，提问作者jenik2205