polyline-complex

Sample code supporting Google Maps Platform JavaScript API documentation. author(s): Geo Developer IX Documentation Team

HTML

<!doctype html>
<!--
 @license
 Copyright 2026 Google LLC. All Rights Reserved.
 SPDX-License-Identifier: Apache-2.0
-->

<html>
  <head>
    <title>Complex Polylines</title>

    <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))})({
            });
    </script>
  </head>
  <body>
    <gmp-map center="41.879, -87.624" zoom="7" map-id="DEMO_MAP_ID"></gmp-map>
  </body>
</html>

CSS

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

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

JavaScript

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

/**
 * This example creates an interactive map which constructs a polyline based on
 * user clicks. Note that the polyline only appears once its path property
 * contains two LatLng coordinates.
 */

let poly;
const mapElement = document.querySelector('gmp-map');
let innerMap;

async function init() {
  // Import the needed libraries.
  const [{ Polyline }, { AdvancedMarkerElement }] = await Promise.all([
    google.maps.importLibrary('maps'),
    google.maps.importLibrary('marker'),
  ]);

  innerMap = mapElement.innerMap;

  poly = new Polyline({
    strokeColor: '#000000',
    strokeOpacity: 1.0,
    strokeWeight: 3,
  });
  poly.setMap(innerMap);

  // Handles click events on a map, and adds a new point to the Polyline.
  innerMap.addListener('click', (event) => {
    const latLng = event.latLng;
    if (!latLng) return;

    const path = poly.getPath();

    // Because path is an MVCArray, we can simply append a new coordinate
    // and it will automatically appear.
    path.push(latLng);

    // Add a new marker at the new plotted point on the polyline.
    new AdvancedMarkerElement({
      position: latLng,
      title: '#' + path.getLength(),
      map: innerMap,
    });
  });
}

void init();