JavaScript Google Maps API: Polyline's 'path' property not initializing correctly

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1

I’m having trouble with the Google Maps JavaScript API. I’m trying to draw a Polyline on a map using an array of LatLngLiterals that updates continuously. But the ‘path’ property of the google.maps.Polyline object isn’t initializing properly.

Here’s what’s weird: even though I include the ‘path’ property when creating the Polyline, it doesn’t exist after the map loads. I can access other properties of the Polyline object, but not ‘path’.

I get this error: ‘Cannot read property ‘push’ of undefined’. I’ve tried setPath(), using LatLng classes, and MVCArray, but nothing works.

Here’s a simplified version of my code:

function initMap() {
  const mapOptions = { zoom: 12, center: { lat: 40.7, lng: -74 } };
  const myMap = new google.maps.Map(document.getElementById('map'), mapOptions);

  const routeCoords = [
    { lat: 40.7, lng: -74 },
    { lat: 40.8, lng: -74.1 },
    { lat: 40.9, lng: -74.2 }
  ];

  const routeLine = new google.maps.Polyline({
    map: myMap,
    path: routeCoords,
    strokeColor: '#FF0000',
    visible: true
  });

  // This line causes the error:
  routeLine.path.push({ lat: 41, lng: -74.3 });
}

Any ideas what I’m doing wrong? Thanks for your help!

2

I’ve run into this exact problem before, and it can be really frustrating. The key is understanding how Google Maps API handles the Polyline’s path internally.

Instead of trying to access the path directly, you need to use the getPath() method, which returns an MVCArray. This array is what you should be manipulating to add or remove points.

Here’s what worked for me:

const routeLine = new google.maps.Polyline({
    map: myMap,
    path: routeCoords,
    strokeColor: '#FF0000',
    visible: true
});

// Add a new point to the path
routeLine.getPath().push(new google.maps.LatLng(41, -74.3));

Also, make sure you’re using the latest version of the API. They’ve made some changes over the years that can catch you off guard if you’re working with older documentation or examples.

If you’re still having issues, double-check your API key and make sure you’ve enabled the correct services in your Google Cloud Console. Sometimes it’s the simple things that trip us up!

3

hey there, i had a similar issue. try using setPath() instead of directly modifying the path. something like this might work:

routeLine.setPath(routeCoords);
routeCoords.push({ lat: 41, lng: -74.3 });
routeLine.setPath(routeCoords);

this way youre updating the whole path at once. hope that helps!

4

I encountered a similar issue when working with the Google Maps API. The problem likely stems from how the Polyline object handles its path property. Instead of directly accessing routeLine.path, try using the getPath() method to retrieve the MVCArray, then use that to modify the path.

Here’s a modified version of your code that should work:

const routeLine = new google.maps.Polyline({
  map: myMap,
  path: routeCoords,
  strokeColor: '#FF0000',
  visible: true
});

// Use getPath() to access the MVCArray
routeLine.getPath().push({ lat: 41, lng: -74.3 });

This approach ensures you’re working with the correct MVCArray object. Additionally, make sure you’re loading the latest version of the Google Maps JavaScript API and that all necessary libraries are included. If the issue persists, double-check your API key and console for any other errors.