node-sqlite3: testing json1 extension

I just installed sqlite3 in nodejs and tried to execute simple program. I got undefined for the returned data.

Code

var sqlite3 = require('sqlite3').verbose();
var db = new sqlite3.Database(':memory:');

db.serialize(function() {
    db.run('SELECT json(?)', JSON.stringify({ok:true}), function(err, data){
        if(err)
            return console.log(err);

        console.log(data);
        db.close();
    });
});

Please correct my code.

via Kiran