Sublayer

// Once the layer loads, check if `supportsAttachment`
// operation is enabled on the layer

layer.when(function(){
  if (layer.capabilities.data.supportsAttachment) {
    // if attachments are enabled on the layer
    setupAttachments();
  }
});

let countiesLyr = layer.sublayers.find(function(sublayer){
  return sublayer.title === "States";
});
countiesLyr.definitionExpression = "STATE = 'Nebraska'"

// add a definition expression to sublayer when
// it is created in MapImageLayer constructor
let layer = new MapImageLayer({
  url: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/USA/MapServer",
  sublayers: [{
    id: 0,
    definitionExpression: "STATE = 'Nebraska'"
  }]
});

// Set a definition expression on the sublayer with ID of 0
layer.findSublayerById(0).definitionExpression = "STATE = 'Nebraska'";

// print the first Sublayer's first field to the console
console.log(mapImageLayer.sublayers.items[0].fields[0]);

// OUTPUT:
alias: "OBJECTID"
defaultValue: undefined
description: "the objectid"
domain: null
editable: false
name: "objectid"
nullable: false
type: "oid"
valueType: null

// lookup a field by name, name is case-insensitive
const fieldsIndex = mapImageLayer.sublayers.items[0].fieldsIndex.get("OBjecTID");

// if there's a field by that name, print it to the console
if (fieldsIndex) {
  console.log("fieldsIndex: ", fieldsIndex);
}

// Creates a MapImageLayer instance containing only the sublayers defined below.
let layer = new MapImageLayer({
  url: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/USA/MapServer",
  // this service has four sublayers, but we're only going to include three.
  sublayers: [ { id: 2 }, { id: 1 }, { id: 0 } ]
});

// Creates a MapImageLayer instance containing only the sublayers defined below.
let layer = new MapImageLayer({
  url: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/USA/MapServer",
  sublayers: [{ // sets a new renderer on this sublayer
    id: 2,
    renderer: {
      type: "class-breaks"  // autocasts as new ClassBreaksRenderer()
      // set renderer properties here
    }
  }, { // sets new labelingInfo on the sublayer
    id: 1,
    labelingInfo: [ new LabelClass( ... ) ]
  }, { // retains properties defined by the service, but makes sublayer not visible
    id: 0,
    visible: false
  }]
});

let layer = new MapImageLayer({
  url: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/USA/MapServer",
  sublayers: [{
    id: 3,
    labelsVisible: true,
    // labelingInfo autocasts to an array of LabelClass objects
    labelingInfo: [{
      labelExpression: "[name]",
      labelPlacement: "always-horizontal",
      symbol: {
        type: "text",  // autocasts as new TextSymbol()
        color: [255, 255, 255, 0.7],
        haloColor: [0, 0, 0, 0.85],
        haloSize: 1,
        font: {
          size: 11
        }
      },
      minScale: 2400000,
      maxScale: 73000
    }]
  }]
});

// turns on labels defined for sublayer 0
layer.findSublayerById(0).labelsVisible = true;

let layer = new MapImageLayer({
  url: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/USA/MapServer",
  sublayers: [
    {
      id: 0,
      minScale: 5000000,
      maxScale: 24000
    },
    {
      id: 1
      minScale: 24000,
      maxScale: 100
    }
  ]
});

let layer = new MapImageLayer({
  url: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/USA/MapServer",
  sublayers: [
    {
      id: 0,
      minScale: 5000000,
      maxScale: 24000
    },
    {
      id: 1,
      minScale: 24000,
      maxScale: 100
    }
  ]
});

// Set the opacity of the layer to 0.5
layer.findSublayerById(0).opacity = 0.5;

let layer = new MapImageLayer({
  url: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/USA/MapServer",
  sublayers: [{
    id: 0,
    popupTemplate: {
      title: "{COUNTY}",
      content: "{POP2007} people lived in this county in 2007"
    }
  }]
});

let layer = new MapImageLayer({
  url: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/USA/MapServer",
  sublayers: [{
    id: 0,
    renderer: {
      type: "simple",  // autocasts as new SimpleRenderer()
      symbol: {
        type: "simple-marker",  // autocasts as new SimpleMarkerSymbol()
        color: "black",
        size: 8
      }
    }
  }]
});

// Creates two sublayers that point to the same map service layer.
// Each layer presents different features in the data using
// definition expressions and renderers.
let mapImageLayer = new MapImageLayer({
  sublayers: [{
    id: 10,
    definitionExpression: "POP < 100000",
    renderer: {
      type: "simple",  // autocasts as new SimpleRenderer()
      symbol: smallMarker
    },
    source: {
      type: "map-layer",
      mapLayerId: 0
    }
  }, {
    id: 11,
    definitionExpression: "POP > 100001",
    renderer: {
      type: "simple",  // autocasts as new SimpleRenderer()
      symbol: largeMarker
    },
    source: {
      type: "map-layer",
      mapLayerId: 0
    }
  }]
});

// test function for determining if a MapImageLayer's sublayers
// contain at least one dynamic data layer
function hasDynamicDataLayer (layer){
  if (layer.sublayers && layer.sublayers.sublayers){
    return layer.sublayers.sublayers.some(function(sublayer){
      return sublayer.source.type === "data-layer";
    });
  } else {
    console.log("layer does not have sublayers or nested sublayers");
    return false;
  }
}

let radarSublayer = layer.sublayers.find(function(sublayer){
  return sublayer.title === "radar";
});

let layer = new MapImageLayer({
  url: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/USA/MapServer",
  sublayers: [{
    // this sublayer is visible by default
    id: 0
  }, {
    // this sublayer will be added to the layer but not visible
    id: 1,
    visible: false
  }]
    // all other sublayers in the service are excluded from the layer
});

let layer = new MapImageLayer({
  url: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/Census/MapServer",
  sublayers: [{
    id: 0,
    renderer: renderer,
      opacity: 0.9,
      source: {
        type: "data-layer",
        dataSource: {
          type: "join-table",
          leftTableSource: {
            type: "map-layer",
            mapLayerId: 3
          },
          rightTableSource: {
            type: "data-layer",
            // references a table in a registered workspace that doesn't have geometries
            dataSource: {
              type: "table",
              workspaceId: "CensusFileGDBWorkspaceID",
              dataSourceName: "ancestry"
            }
          },
          leftTableKey: "STATE_NAME",
          rightTableKey: "State",
          joinType: "left-outer-join"
        }
      }
    }
  ]
});

// Creates two sublayers that point to the same map service layer.
// Each layer presents different features in the data using
// definition expressions and renderers.
let mapImageLayer = new MapImageLayer({
  sublayers: [{
    id: 10,
    definitionExpression: "POP < 50000",
    renderer: {
      type: "class-breaks"  // autocasts as new ClassBreaksRenderer()
      // set renderer properties here
    },
    source: {
      type: "map-layer",
      mapLayerId: 0
    }
  }, {
    id: 11,
    definitionExpression: "GRADUATED_HS > 0.449",
    renderer: {
      type: "class-breaks"  // autocasts as new ClassBreaksRenderer()
      // set renderer properties here
    },
    source: {
      type: "map-layer",
      mapLayerId: 0
    }
  }]
});

let layer = new MapImageLayer({
  url: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/Census/MapServer",
  sublayers: [{
    id: 0,
    renderer: renderer,
    opacity: 0.9,
    source: {
      type: "data-layer",
      dataSource: {
        type: "join-table",
        leftTableSource: {
          type: "map-layer",
          mapLayerId: 3
        },
        rightTableSource: {
          type: "data-layer",
          dataSource: {
            type: "table",
            workspaceId: "CensusFileGDBWorkspaceID",
            dataSourceName: "ancestry"
          }
        },
        leftTableKey: "STATE_NAME",
        rightTableKey: "State",
        joinType: "left-outer-join"
      }
    }
  }]
});

let layer = new MapImageLayer({
  url: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/USA/MapServer",
  sublayers: [{
    title: "Places",
    renderer: renderer,
    source: {
      type: "data-layer",
      dataSource: {
        type: "query-table",
        workspaceId: "MyDatabaseWorkspaceIDSSR2",
        query: "SELECT * FROM ss6.gdb.Places",
        oidFields: "objectid"
      }
    }
  }]
});

let layer = new MapImageLayer({
  url: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/Elevation/GlacierBay/MapServer",
  sublayers: [{
    title: "slope",
    opacity: 0.75,
    source: {
      type: "data-layer",
      dataSource: {
        type: "raster",
        workspaceId: "MyDatabaseWorkspaceIDSSR2",
        dataSourceName: "slope.tiff"
      }
    }
  }]
});

let layer = new MapImageLayer({
   url: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/USA/MapServer",
   sublayers: [{
     renderer: renderer,
     source: {
       type: "data-layer",
       dataSource: {
         type: "table",
         workspaceId: "MyDatabaseWorkspaceIDSSR2",
         dataSourceName: "ss6.gdb.Railroads"
       }
     }
   }]
 });