You can update a document by using the upsert() or replace() methods.

The replace() method replaces a document that already exists with new contents. The upsert() method creates the document if it does not already exist.

The following example shows how to update a document by using the replace() method:

var myBucket = myCluster.openBucket();
myBucket.replace('document_name', {some: 'value'}, function(err, res) {
  if (err) {
    console.log('operation failed', err);
    /*
    operation failed { [Error: The key does not exist on the server] code: 13 }
    */
    return;
  }

  console.log('success!', res);
});

Sample output from the example:

success! { cas: { '0': 3085434880, '1': 1662465098 } }