Google Maps JS on Map Load - Javascript

Introduction

Google Maps JS is a popular way to add maps and location-based services to your web applications. One of the key features of Google Maps JS is the ability to load data onto the map when it loads, such as markers, polygons, and other features. In this tutorial, we'll cover how to load data onto a Google Map when it loads using Javascript.

Prerequisites

Before we start, you'll need a few things:

• A Google Maps API key
• A basic understanding of Javascript
• A web application with a Google Map already embedded

Adding Data to the Map on Load

In order to add data to a Google Map on load, we'll need to use the addListenerOnce() function to wait for the map to finish loading, and then add our data to the map. Here's an example:

google.maps.event.addListenerOnce(map, 'idle', function(){

  // Add your code to add data to the map here

});

In this code, we're using the addListenerOnce() function to listen for the idle event, which fires when the map has finished loading. Once the event fires, our function will execute, and we can then add data to the map using the map variable.

Examples

Add a Marker to the Map on Load

google.maps.event.addListenerOnce(map, 'idle', function(){
  var marker = new google.maps.Marker({
    position: new google.maps.LatLng(37.774929, -122.419416),
    map: map,
    title: 'San Francisco'
  });
});

In this example, we're adding a marker to our map, positioned at the coordinates for San Francisco. We pass the map variable to the marker as the map on which it should be displayed.

Add a Polygon to the Map on Load

google.maps.event.addListenerOnce(map, 'idle', function(){
  var polygon = new google.maps.Polygon({
    paths: [
      new google.maps.LatLng(37.774929, -122.419416),
      new google.maps.LatLng(37.774929, -122.529416),
      new google.maps.LatLng(37.664929, -122.529416),
      new google.maps.LatLng(37.664929, -122.419416)
    ],
    strokeColor: '#FF0000',
    strokeOpacity: 0.8,
    strokeWeight: 2,
    fillColor: '#FF0000',
    fillOpacity: 0.35
  });
  polygon.setMap(map);
});

In this example, we're adding a polygon to our map, with vertices at the coordinates for San Francisco. We set the strokeColor, strokeOpacity, strokeWeight, fillColor, and fillOpacity properties to customize the appearance of the polygon.

Conclusion

In this tutorial, we've covered how to add data to a Google Map when it loads using Javascript. By using the addListenerOnce() function, we can wait for the map to finish loading and then execute code to add data to the map. This opens up a lot of possibilities for customizing the appearance and functionality of maps in your web applications.