import { Storage } from '@google-cloud/storage';

const gcs = new Storage({
    projectId: // ...,
    credentials: // ...
});
const bucket = gcs.bucket('my-bucket');

async function run() {
    const path = 'some/file';
    const content1 = 'some-content';

    const file = bucket.file(path);
    await file.save(Buffer.from(content1), {
        resumable: false,
        validation: false
     });

    const [readContent1] = await file.download({
        validation: false,
    });

    readContent1.toString('utf8') === content1; // true

    const content2 = 'some-other-content';
    await file.save(Buffer.from(content2), {
        resumable: false,
        validation: false
     });

    const [readContent2] = await file.download({
        // This is necessary to check the content of the second download, otherwise it throws with:
        // "The downloaded data did not match the data from the server. To be sure the content is the same, you should download the file again."
        validation: false
    });

    readContent2.toString('utf8') === content2; // false
    // readContent2 === 'some-contentsome-o'
}

run();