google drive sdk - How to upload a simple file through JavaScript

• Here are explained all types of uploads you can do with Google Drive API.
• My code does a multipart upload with a client-side request using v3 Google Drive API. You can do it server-side as well.
• In the metadata object parents property can be used to upload file to a specific folder. It's not mandatory.

const fileToUpload = inputUpload.files[0];

var metadata = {
  name: fileToUpload.name,
  mimeType: fileToUpload.type
  //parents: ["folderID"]
};

var formData = new FormData();
formData.append( "metadata", new Blob( [JSON.stringify( metadata )], {type: "application/json"} ));
formData.append( "file", fileToUpload );

fetch( "https://www.googleapis.com/upload/drive/v3/files?uploadType=multipart", {
  method: "POST",
  headers: new Headers({ "Authorization": "Bearer " + gapi.auth.getToken().access_token }),
  body: formData
}).then( function( response ){
  return response.json();
}).then( function( value ){
  console.log( value );
});

In order to make work this code, you have to be been authorized with OAuth 2.0.

• Here you can find an example of authentication and here a better explanation on authentication. Both links are from APIs documentation.

Anyway a similar question had been already answered.