This example creates the traditional "bounce-drop" animation using CSS and
advanced markers. In the `IntersectionObserver`, it adds the
`drop` CSS style. The `IntersectionObserver`sees when each marker enters the
viewport, and adds the style. Then, the `animationend` event listener that the
`createMarker()` function added to each marker removes the style.

Read the
[documentation](https://developers.google.com/maps/documentation/javascript/advanced-markers/html-markers.md.txt).
<iframe src="https://maps-docs-team.web.app/samples/advanced-markers-animation/dist/" allow="fullscreen; "></iframe>

### TypeScript

```typescript
/**
 * Returns a random lat lng position within the map bounds.
 */
function getRandomPosition(map: google.maps.Map): google.maps.LatLngLiteral {
    const bounds = map.getBounds()!;
    const minLat = bounds.getSouthWest().lat();
    const minLng = bounds.getSouthWest().lng();
    const maxLat = bounds.getNorthEast().lat();
    const maxLng = bounds.getNorthEast().lng();

    const latRange = maxLat - minLat;

    // Note: longitude can span from a positive longitude in the west to a
    // negative one in the east. e.g. 150lng (150E) <-> -30lng (30W) is a large
    // span that covers the whole USA.
    let lngRange = maxLng - minLng;
    if (maxLng < minLng) {
        lngRange += 360;
    }

    return {
        lat: minLat + Math.random() * latRange,
        lng: minLng + Math.random() * lngRange,
    };
}

const intersectionObserver = new IntersectionObserver((entries) => {
    for (const entry of entries) {
        if (entry.isIntersecting) {
            entry.target.classList.add('drop');
            intersectionObserver.unobserve(entry.target);
        }
    }
});

async function init(): Promise<void> {
    // Request needed libraries.
    const [
        { Map },
        { event, ControlPosition },
        { AdvancedMarkerElement, PinElement },
    ] = await Promise.all([
        google.maps.importLibrary('maps'),
        google.maps.importLibrary('core'),
        google.maps.importLibrary('marker'),
    ]);

    const position = { lat: 37.4242011827985, lng: -122.09242296450893 };

    const map = new Map(document.getElementById('map')!, {
        zoom: 14,
        center: position,
        mapId: '4504f8b37365c3d0',
    });

    // Create 100 markers to animate.
    event.addListenerOnce(map, 'idle', () => {
        for (let i = 0; i < 100; i++) {
            createMarker(map, AdvancedMarkerElement, PinElement);
        }
    });

    // Add a button to reset the example.
    const controlDiv = document.createElement('div');
    const controlUI = document.createElement('button');

    controlUI.classList.add('ui-button');
    controlUI.innerText = 'Reset the example';
    controlUI.addEventListener('click', () => {
        // Reset the example by recreating the map.
        refreshMap();
    });
    controlDiv.appendChild(controlUI);
    map.controls[ControlPosition.TOP_CENTER].push(controlDiv);
}

function createMarker(
    map: google.maps.Map,
    AdvancedMarkerElement: typeof google.maps.marker.AdvancedMarkerElement,
    PinElement: typeof google.maps.marker.PinElement
) {
    const content = new PinElement();
    new AdvancedMarkerElement({
        position: getRandomPosition(map),
        map,
        content,
    });

    content.style.opacity = '0';
    content.addEventListener('animationend', () => {
        content.classList.remove('drop');
        content.style.opacity = '1';
    });
    const time = 2 + Math.random(); // 2s delay for easy to see the animation
    content.style.setProperty('--delay-time', time + 's');
    intersectionObserver.observe(content);
}

function refreshMap() {
    // Refresh the map.
    const mapContainer = document.getElementById('mapContainer');
    const map = document.getElementById('map');
    map!.remove();
    const mapDiv = document.createElement('div');
    mapDiv.id = 'map';
    mapContainer!.appendChild(mapDiv);
    void init();
}

void init();
```

### JavaScript

```javascript
/**
 * Returns a random lat lng position within the map bounds.
 */
function getRandomPosition(map) {
    const bounds = map.getBounds();
    const minLat = bounds.getSouthWest().lat();
    const minLng = bounds.getSouthWest().lng();
    const maxLat = bounds.getNorthEast().lat();
    const maxLng = bounds.getNorthEast().lng();

    const latRange = maxLat - minLat;

    // Note: longitude can span from a positive longitude in the west to a
    // negative one in the east. e.g. 150lng (150E) <-> -30lng (30W) is a large
    // span that covers the whole USA.
    let lngRange = maxLng - minLng;
    if (maxLng < minLng) {
        lngRange += 360;
    }

    return {
        lat: minLat + Math.random() * latRange,
        lng: minLng + Math.random() * lngRange,
    };
}

const intersectionObserver = new IntersectionObserver((entries) => {
    for (const entry of entries) {
        if (entry.isIntersecting) {
            entry.target.classList.add('drop');
            intersectionObserver.unobserve(entry.target);
        }
    }
});

async function init() {
    // Request needed libraries.
    const [
        { Map },
        { event, ControlPosition },
        { AdvancedMarkerElement, PinElement },
    ] = await Promise.all([
        google.maps.importLibrary('maps'),
        google.maps.importLibrary('core'),
        google.maps.importLibrary('marker'),
    ]);

    const position = { lat: 37.4242011827985, lng: -122.09242296450893 };

    const map = new Map(document.getElementById('map'), {
        zoom: 14,
        center: position,
        mapId: '4504f8b37365c3d0',
    });

    // Create 100 markers to animate.
    event.addListenerOnce(map, 'idle', () => {
        for (let i = 0; i < 100; i++) {
            createMarker(map, AdvancedMarkerElement, PinElement);
        }
    });

    // Add a button to reset the example.
    const controlDiv = document.createElement('div');
    const controlUI = document.createElement('button');

    controlUI.classList.add('ui-button');
    controlUI.innerText = 'Reset the example';
    controlUI.addEventListener('click', () => {
        // Reset the example by recreating the map.
        refreshMap();
    });
    controlDiv.appendChild(controlUI);
    map.controls[ControlPosition.TOP_CENTER].push(controlDiv);
}

function createMarker(map, AdvancedMarkerElement, PinElement) {
    const content = new PinElement();
    new AdvancedMarkerElement({
        position: getRandomPosition(map),
        map,
        content,
    });

    content.style.opacity = '0';
    content.addEventListener('animationend', () => {
        content.classList.remove('drop');
        content.style.opacity = '1';
    });
    const time = 2 + Math.random(); // 2s delay for easy to see the animation
    content.style.setProperty('--delay-time', time + 's');
    intersectionObserver.observe(content);
}

function refreshMap() {
    // Refresh the map.
    const mapContainer = document.getElementById('mapContainer');
    const map = document.getElementById('map');
    map.remove();
    const mapDiv = document.createElement('div');
    mapDiv.id = 'map';
    mapContainer.appendChild(mapDiv);
    void init();
}

void init();
```

### CSS

```css
/* 
 * Always set the map height explicitly to define the size of the div element
 * that contains the map. 
 */
#map {
    height: 100%;
}

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

/* set the default transition time */
:root {
    --delay-time: 0.5s;
}

#map {
    height: 100%;
}

#mapContainer {
    height: 100%;
}

@keyframes drop {
    0% {
        transform: translateY(-200px) scaleY(0.9);
        opacity: 0;
    }
    5% {
        opacity: 0.7;
    }
    50% {
        transform: translateY(0px) scaleY(1);
        opacity: 1;
    }
    65% {
        transform: translateY(-17px) scaleY(0.9);
        opacity: 1;
    }
    75% {
        transform: translateY(-22px) scaleY(0.9);
        opacity: 1;
    }
    100% {
        transform: translateY(0px) scaleY(1);
        opacity: 1;
    }
}
.drop {
    animation: drop 0.3s linear forwards var(--delay-time);
}

.ui-button {
    background-color: #fff;
    border: 0;
    border-radius: 2px;
    box-shadow: 0 1px 4px -1px rgba(0, 0, 0, 0.3);
    margin: 10px;
    padding: 0 0.5em;
    font:
        400 18px Roboto,
        Arial,
        sans-serif;
    overflow: hidden;
    height: 40px;
    cursor: pointer;
}

.ui-button:hover {
    background: rgb(235, 235, 235);
}
```

### HTML

```html
<html>
    <head>
        <title>Advanced Markers CSS Animation</title>

        <link rel="stylesheet" type="text/css" href="./style.css" />
        <script type="module" src="./index.js"></script>
        <script>
            // prettier-ignore
            (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: "GOOGLE_MAPS_API_KEY"
            });
        </script>
    </head>
    <body>
        <div id="mapContainer">
            <div id="map" style="height: 100%"></div>
        </div>
    </body>
</html>
```

### Try Sample

[JSFiddle.net](https://jsfiddle.net/gh/get/library/pure/googlemaps-samples/js-api-samples/tree/main/dist/samples/advanced-markers-animation/jsfiddle)

### Clone Sample


Git and Node.js are required to run this sample locally. Follow these [instructions](https://docs.npmjs.com/downloading-and-installing-node-js-and-npm)
to install Node.js and NPM. You will also need a [Google Maps API key](https://developers.google.com/maps/documentation/javascript/get-api-key.md.txt).


The following commands clone the repository, install dependencies, and copy the environment file.

```javascript
  git clone https://github.com/googlemaps-samples/js-api-samples.git
  cd js-api-samples
  npm i
  cp .env.template .env
```


Once you copy the environment file, make sure to open the `.env` file and replace `<Insert your own development API key here>` with your actual API key before starting the sample.

```javascript
  cd samples/advanced-markers-animation
  npm start
```