ideas.js

class MongoOptions () {
    static parse () {
      // does all the parsing without async eg DNS checking operations
    }
    
    static performAsync () {
      // follow up handler to check eg DNS (async) tasks
    }
    
    static parseAsync () {
      // does parsing with 
    }
}

class MongoClient () {
    constructor (uri, options = defaultOptions) {
      this.parsedOptions = MongoOptions.parse()
    }
    connection (uri, options = defaultOptions, callback) {
      MongoOptions.parseAsync(uri, options, (parsedOptions) => {
        
      })
    }
}