Google Drive API V3 (javascript) update file contents

Question

I want to update the contents of a Google doc using the Google Drive API V3 (javascript):

https://developers.google.com/drive/v3/reference/files/update

I'm able to update the file metadata (such as the name) but the documentation doesn't include patch semantics for the actual file content. Is there a way to pass a JSON.stringify() value as a param in the gapi.client.drive.files.update request:

var request = gapi.client.drive.files.update({
    'fileId': fileId,
    'name' : 'Updated File Name',
    'uploadType': 'media',
    'mimeType' : 'application/vnd.google-apps.document'
  });

var fulfilledCallback = function(fulfilled) { 
    console.log("Update fulfilled!", fulfilled);
};
var rejectedCallback = function(rejected) { 
    console.log("Update rejected!", rejected);
};

request.then(fulfilledCallback, rejectedCallback)

Answer 1

There are two issues:

1. The JavaScript client library doesn't support media upload.
2. Google Docs files don't have a native file format.

You can work around issue #1 by writing your own upload functionality built on top of XHR. The following code should work on most modern web browsers:

function updateFileContent(fileId, contentBlob, callback) {
  var xhr = new XMLHttpRequest();
  xhr.responseType = 'json';
  xhr.onreadystatechange = function() {
    if (xhr.readyState != XMLHttpRequest.DONE) {
      return;
    }
    callback(xhr.response);
  };
  xhr.open('PATCH', 'https://www.googleapis.com/upload/drive/v3/files/' + fileId + '?uploadType=media');
  xhr.setRequestHeader('Authorization', 'Bearer ' + gapi.auth.getToken().access_token);
  xhr.send(contentBlob);
}

To work around issue #2 you can send Drive a file type that Google Docs can import from, such .txt, .docx, etc. The following code uses the function above to update the content of a Google Doc using plain text:

function run() {
  var docId = '...';
  var content = 'Hello World';
  var contentBlob = new  Blob([content], {
    'type': 'text/plain'
  });
  updateFileContent(fileId, contentBlob, function(response) {
    console.log(response);
  });
}