How to use filter on the Search widget in ArcGIS JS API 4.9?

Question

var searchWidget = new Search({
  view: view,
  includeDefaultSources:false
  sources: [{
    locator: new Locator({ url: "https://geocode.arcgis.com/arcgis/rest/services/World/GeocodeServer"}),
    countryCode:"GB",
    categories:["Address", "Postal"],
    maxResults: 10
    minSuggestCharacters: 4,
    placeholder:"Find address",
    filter:{
        ...
    }
  }]
});

I'm trying to limit the results to a certain geographical area. I've been told I can use the filter property, but I can't find how or any examples.

Answer 1

The filter object can have a geometry or where property. The full specification for this object can be found here. So for example if you want to filter to the USA lower 48 states you might send in a Polygon into the geometry property like this:

filter: {
  geometry: new Polygon({
    "rings": [
      [
        [
          -124.60937499999179,
          48.17147426999536
        ],
        [
          -110.5468749999955,
          49.33038796569682
        ],
        [
          -66.0742187500073,
          48.17147426999536
        ],
        [
          -70.99609375000601,
          24.454504932416402
        ],
        [
          -125.66406249999149,
          30.682664491952345
        ],
        [
          -124.60937499999179,
          48.17147426999536
        ]
      ]
    ],
    "spatialReference": {
      "wkid": 4326
    }
  })
}

See the working example here. To see it in action, search "Rome" with the filter in place, and then without.

Note that even if you're sending in a Polygon like I am above, it is translated into a rectangle bounding box because that is what the Geocoding service accepts.