Make data features respond to mouse events

This sample shows how to make data features respond to mouse events.

Read the documentation.

TypeScript

const mapElement = document.querySelector('gmp-map') as google.maps.MapElement;
let innerMap;
let lastInteractedFeatureIds: string[] = [];
let lastClickedFeatureIds: string[] = [];
let datasetLayer;

// Note, 'globalid' is an attribute in this Dataset.
function handleClick(/* MouseEvent */ e) {
    if (e.features) {
        lastClickedFeatureIds = e.features.map(
            (f) => f.datasetAttributes['globalid']
        );
    }
    datasetLayer.style = applyStyle;
}

function handleMouseMove(/* MouseEvent */ e) {
    if (e.features) {
        lastInteractedFeatureIds = e.features.map(
            (f) => f.datasetAttributes['globalid']
        );
    }
    datasetLayer.style = applyStyle;
}

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

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

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

    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;
        }
    });
}

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(/* FeatureStyleFunctionOptions */ params) {
    const datasetFeature = params.feature;

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

    if (
        lastInteractedFeatureIds.includes(
            datasetFeature.datasetAttributes['globalid']
        )
    ) {
        return styleMouseMove;
    }
    return styleDefault;
}

initMap();
index.ts

JavaScript

const mapElement = document.querySelector('gmp-map');
let innerMap;
let lastInteractedFeatureIds = [];
let lastClickedFeatureIds = [];
let datasetLayer;
// Note, 'globalid' is an attribute in this Dataset.
function handleClick(/* MouseEvent */ e) {
    if (e.features) {
        lastClickedFeatureIds = e.features.map((f) => f.datasetAttributes['globalid']);
    }
    datasetLayer.style = applyStyle;
}
function handleMouseMove(/* MouseEvent */ e) {
    if (e.features) {
        lastInteractedFeatureIds = e.features.map((f) => f.datasetAttributes['globalid']);
    }
    datasetLayer.style = applyStyle;
}
async function initMap() {
    // 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';
    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;
        }
    });
}
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(/* FeatureStyleFunctionOptions */ params) {
    const datasetFeature = params.feature;
    // Note, 'globalid' is an attribute in this dataset.
    if (lastClickedFeatureIds.includes(datasetFeature.datasetAttributes['globalid'])) {
        return styleClicked;
    }
    if (lastInteractedFeatureIds.includes(datasetFeature.datasetAttributes['globalid'])) {
        return styleMouseMove;
    }
    return styleDefault;
}
initMap();
index.js

CSS

/* 
 * Optional: Makes the sample page fill the window. 
 */
html,
body {
    height: 100%;
    margin: 0;
    padding: 0;
}

#attribution {
    background-color: rgba(255, 255, 255, 0.7);
    font-family: 'Roboto', 'Arial', 'sans-serif';
    font-size: 10px;
    padding: 2px;
    margin: 2px;
}
style.css

HTML

<html>
    <head>
        <title>Style a polygon data feature</title>

        <link rel="stylesheet" type="text/css" href="./style.css" />
        <script type="module" src="./index.js"></script>
        <!-- prettier-ignore -->
        <script>(g=>{var h,a,k,p="The Google Maps JavaScript API",c="google",l="importLibrary",q="__ib__",m=document,b=window;b=b[c]||(b[c]={});var d=b.maps||(b.maps={}),r=new Set,e=new URLSearchParams,u=()=>h||(h=new Promise(async(f,n)=>{await (a=m.createElement("script"));e.set("libraries",[...r]+"");for(k in g)e.set(k.replace(/[A-Z]/g,t=>"_"+t[0].toLowerCase()),g[k]);e.set("callback",c+".maps."+q);a.src=`https://maps.${c}apis.com/maps/api/js?`+e;d[q]=f;a.onerror=()=>h=n(Error(p+" could not load."));a.nonce=m.querySelector("script[nonce]")?.nonce||"";m.head.append(a)}));d[l]?console.warn(p+" only loads once. Ignoring:",g):d[l]=(f,...n)=>r.add(f)&&u().then(()=>d[l](f,...n))})
        ({key: "AIzaSyA6myHzS10YXdcazAFalmXvDkrYCp5cLc8", v: "weekly"});</script>
    </head>
    <body>
        <gmp-map
            center="40.780101, -73.967780"
            zoom="13"
            map-id="5cd2c9ca1cf05670"
            map-type-control="false">
            <div id="attribution" slot="control-block-end-inline-start">
                Data source: NYC Open Data
            </div>
        </gmp-map>
    </body>
</html>
index.html

Try Sample

Clone Sample

Git and Node.js are required to run this sample locally. Follow these instructions to install Node.js and NPM. The following commands clone, install dependencies and start the sample application. 

  git clone https://github.com/googlemaps-samples/js-api-samples.git
  cd samples/dds-datasets-polygon-click
  npm i
  npm start