Cors Policy Error when sending Authentication Bearer token - node.js (Google cloud functions)

Question

I am trying to communicate to my cloud function from a chrome plugin. Everything works fine if i don't enable authentication in the cloud function console. But when i enable only authenticated user then I get the following error

Access to XMLHttpRequest at has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource

My Ajax code

 return new Promise((resolve, reject) => {

    $.ajax({
      url : API_ENDPOINT+'method4',
      method : 'POST',
      beforeSend: function (xhr) {
          xhr.setRequestHeader('Authorization', 'Bearer '+firebase.auth().currentUser._lat);
      },
      data : 'id='+id,
      success: function(data, textStatus, xhr) {
          console.log(data);
          resolve(data);
      },
      error: function(data, textStatus, xhr) {
          reject(data);
          console.log(data)
      },
  });

});

Below is my Function code deployed on cloud function

exports.method4 = functions.https.onRequest((request, response) =>{

    response.set('Access-Control-Allow-Origin', 'chrome-extension://pcpjkilopmjdhcigjjndndibccdingcb');
    response.set('Access-Control-Allow-Credentials', 'true');

    if (request.method === 'OPTIONS') {

      // Send response to OPTIONS requests
      response.set('Access-Control-Allow-Methods', 'GET, POST');
      response.set('Access-Control-Allow-Headers', 'Authorization');
      response.set('Access-Control-Max-Age', '3600');
      response.status(204).send('');

    } else {

      if (request.method !== 'POST') {
        // Return a "method not allowed" error
        return response.status(405).end();
      }

      return response.send(request.body['id']);

    }
})

I am stuck with this for the past 2 days and not sure what is causing this issue. Thanks in advance.

Answer 1

It seems like your problem is because of the OPTIONS method you are using. As you can see here , the only HTTP methods supported by Google apps scripts web-application are POST and GET and OPTIONS method is currently not supported.