how to authenticate google apis in node.js

Go to the Google Cloud Console and create a new project or select an existing one. You may need to provide a credit card for verification, even though the Google Sheets API is free.

Navigate to the APIs & Services section, search for the Google Sheets API, and enable it for your project. This step allows your application to access the Sheets API.

In the Credentials section, create a new service account key, which will generate a JSON file containing your credentials. This file will be used to authenticate your application with the Google APIs.

Run `npm install google-auth-library` to install the package that simplifies the authentication process with Google APIs in Node.js.

Load the JSON credentials file you downloaded from the Google Cloud Console. You can store the path to this file in an environment variable for security purposes.

Use the `google.auth.getClient()` method from the google-auth-library package to authenticate your application with the loaded credentials. Specify the required API scopes to grant access permissions.

Import the specific Google API client library you want to use, such as the Google Sheets API client library (`google-auth-library/sheets`).

Create an instance of the API client by passing the authenticated client object from the previous step as the `auth` parameter.

Use the API client instance to make requests to the Google API, such as reading or writing data to a Google Sheet. Refer to the API documentation for available methods and parameters.