I am wondering if it is possible to use JavaScript to upload files directly to Google Cloud without having to use Node.js or anything else. I keep searching online but all I find are tutorials with Node.js.
As mentioned by John Hanley :
For objects smaller than a few hundred MB, yes, you can easily write an upload function in pure JavaScript. When objects are large (>100MB) then you need to implement multipart uploads and that gets complicated quickly.
You can refer to the link where a complete description of how to upload files in Google cloud storage using Javascript. You can also generate signed URL for file upload. You can try multi part upload for the large size uploads where mentioned:
XML API multipart uploads in Cloud Storage. This upload method uploads files in parts and then assembles them into a single object using a final request. XML API multipart uploads are compatible with Amazon S3 multipart uploads.
For more information You can refer to the stackoverflow answer, where various methods for the uploading and tracking the progress of files in cloud storage have been mentioned.