Nodejs - rethinkdb Unhandled rejection ReqlDriverError: First argument to `run` must be an open connection

Run simple code as per official document, but getting error

const r = require('rethinkdb');
    var connection = null;
    r.connect( {host: 'localhost', port: 28015}, function(err, conn) {
        if (err) throw err;
        connection = conn;
    })
    
    // r.dbCreate("blog").run(connection, function(err, result) {
    //   if (err) throw err;
    //   console.log(result);
    // });

    r.db('test').tableCreate('authors').run(connection, function(err, result) {
      if (err) throw err;
        console.log(JSON.stringify(result, null, 2));
    })

Unhandled rejection ReqlDriverError: First argument to run must be an open connection. at ReqlDriverError.ReqlError [as constructor] (/Users/tejastank/source/electronjs/website-scanner/node_modules/rethinkdb/errors.js:23:13) at new ReqlDriverError (/Users/tejastank/source/electronjs/website-scanner/node_modules/rethinkdb/errors.js:68:50) at Function.TermBase.run (/Users/tejastank/source/electronjs/website-scanner/node_modules/rethinkdb/ast.js:133:29) at HTMLButtonElement. (file:///Users/tejastank/source/electronjs/website-scanner/index.js:59:41) (node:45504) [DEP0005] DeprecationWarning: Buffer() is deprecated due to security and usability issues. Please use the Buffer.alloc(), Buffer.allocUnsafe(), or Buffer.from() methods instead.

Solution

connection is populated in the .connect() callback, it's not guaranteed to be available exactly after the call. You need to work inside callbacks:

const r = require('rethinkdb');
r.connect( {host: 'localhost', port: 28015}, function(err, conn) {
    if (err) throw err;

    r.db('test').tableCreate('authors').run(conn, function(err, result) {
        if (err) throw err;
        console.log(JSON.stringify(result, null, 2));
    });
});

or by using promises:

const r = require('rethinkdb');
r.connect({host: 'localhost', port: 28015})
    .then(function(conn) {
        return r.db('test').tableCreate('authors').run(conn);
    })
    .then(function(result) {
        console.log(JSON.stringify(result, null, 2));
    });