index.ts

/**
 * @license
 * Copyright 2026 Google LLC. All Rights Reserved.
 * SPDX-License-Identifier: Apache-2.0
 */

// [START maps_dds_datasets_polygon_click]
const mapElement = document.querySelector('gmp-map')!;
let innerMap: google.maps.Map;
let lastInteractedFeatureIds: string[] = [];
let lastClickedFeatureIds: string[] = [];
let datasetLayer: google.maps.FeatureLayer;

// [START maps_dds_datasets_polygon_click_eventhandler]
// Note, 'globalid' is an attribute in this Dataset.
function handleClick(event: google.maps.FeatureMouseEvent) {
    lastClickedFeatureIds = event.features.map(
        (f) => (f as google.maps.DatasetFeature).datasetAttributes.globalid
    );
    datasetLayer.style = applyStyle;
}

function handleMouseMove(event: google.maps.FeatureMouseEvent) {
    lastInteractedFeatureIds = event.features.map(
        (f) => (f as google.maps.DatasetFeature).datasetAttributes.globalid
    );
    datasetLayer.style = applyStyle;
}
// [END maps_dds_datasets_polygon_click_eventhandler]

async function init() {
    // Request needed libraries.
    await google.maps.importLibrary('maps');

    // Get the inner map.
    innerMap = mapElement.innerMap;

    // Dataset ID for NYC park data.
    const datasetId = 'a75dd002-ad20-4fe6-af60-27cd2ed636b4';

    // [START maps_dds_datasets_polygon_click_addlistener]
    datasetLayer = innerMap.getDatasetFeatureLayer(datasetId);
    datasetLayer.style = applyStyle;

    datasetLayer.addListener('click', handleClick);
    datasetLayer.addListener('mousemove', handleMouseMove);

    // Map event listener.
    innerMap.addListener('mousemove', () => {
        // If the map gets a mousemove, that means there are no feature layers
        // with listeners registered under the mouse, so we clear the last
        // interacted feature ids.
        if (lastInteractedFeatureIds.length) {
            lastInteractedFeatureIds = [];
            datasetLayer.style = applyStyle;
        }
    });
    // [END maps_dds_datasets_polygon_click_addlistener]
}

// [START maps_dds_datasets_polygon_click_stylefunction]
const styleDefault = {
    strokeColor: 'green',
    strokeWeight: 2.0,
    strokeOpacity: 1.0,
    fillColor: 'green',
    fillOpacity: 0.3,
};

const styleClicked = {
    ...styleDefault,
    strokeColor: 'blue',
    fillColor: 'blue',
    fillOpacity: 0.5,
};

const styleMouseMove = {
    ...styleDefault,
    strokeWeight: 4.0,
};

function applyStyle(params: google.maps.FeatureStyleFunctionOptions) {
    const datasetFeature = params.feature;

    // Note, 'globalid' is an attribute in this dataset.
    if (
        lastClickedFeatureIds.includes(
            (datasetFeature as google.maps.DatasetFeature).datasetAttributes
                .globalid
        )
    ) {
        return styleClicked;
    }

    if (
        lastInteractedFeatureIds.includes(
            (datasetFeature as google.maps.DatasetFeature).datasetAttributes
                .globalid
        )
    ) {
        return styleMouseMove;
    }
    return styleDefault;
}
// [END maps_dds_datasets_polygon_click_stylefunction]

void init();
// [END maps_dds_datasets_polygon_click]