@types/google.maps: Cannot find name 'google'

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05-10-2024

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TypeScript Trouble: "Cannot find name 'google'" in @types/google.maps

Problem: You're working on a TypeScript project that utilizes the Google Maps API, and you've installed the necessary type definitions (@types/google.maps). However, you're encountering the error "Cannot find name 'google'" when trying to use the Google Maps API in your code.

Simplified Explanation: This error arises because TypeScript needs to know the structure and properties of the Google Maps API to provide type safety. While the @types/google.maps package provides these definitions, your project might not be configured correctly to use them.

Scenario & Code:

Let's say you have a simple TypeScript file (map.ts) where you try to initialize a Google Maps object:

// map.ts
const map = new google.maps.Map(document.getElementById('map'), {
  center: { lat: 40.7128, lng: -74.0060 },
  zoom: 10
});

When you try to compile this file, you receive the "Cannot find name 'google'" error.

Analysis & Clarification:

The error occurs because TypeScript cannot find the google global object, which contains the maps namespace and its various classes. The @types/google.maps package only provides the type definitions. You still need to include the actual Google Maps API script in your HTML file for TypeScript to recognize the google object.

Solution:

1. Include the Google Maps API Script: In your HTML file (e.g., index.html), add the following script tag before the closing </body> tag:

   <script src="https://maps.googleapis.com/maps/api/js?key=YOUR_API_KEY&callback=initMap" async defer></script>
   

   • Replace YOUR_API_KEY with your actual Google Maps API key. You can obtain a key from the Google Cloud Console (https://console.cloud.google.com/).
   • callback=initMap: This specifies a function that will be called after the Google Maps API script loads.

2. Define the initMap Function: In your TypeScript file (map.ts), define the initMap function:

   // map.ts
   declare const google: any; // Declare the global 'google' object
   
   function initMap() {
     const map = new google.maps.Map(document.getElementById('map'), {
       center: { lat: 40.7128, lng: -74.0060 },
       zoom: 10
     });
   }
   

   • declare const google: any;: This tells TypeScript that a global google object exists.
   • initMap Function: This function will be called by the Google Maps API script once it loads, allowing you to initialize your map.

Additional Value:

• any Type: While we're using the any type for google, it's recommended to use the type definitions provided by @types/google.maps for better type safety. You can explore the type definitions to define more specific types for your Google Maps objects and properties.
• Module Augmentation: You can also use module augmentation to extend the google.maps namespace with your own types and functions, further enhancing type safety.

References and Resources:

• Google Maps API Documentation: https://developers.google.com/maps/documentation/javascript/
• @types/google.maps: https://www.npmjs.com/package/@types/google.maps
• TypeScript Documentation: https://www.typescriptlang.org/

By following these steps and understanding the underlying concepts, you can effectively resolve the "Cannot find name 'google'" error and leverage the Google Maps API within your TypeScript projects.