Question

consider this baby simple piece of code

pg.connect( {
    user: 'hhope',
    password: '...',
    port: 5432,
    host: '/var/run/postgresql',
    database: 'phiddler' },
  function( err, client ) {
    client.query(
      "select count(1) as ct from pg_prepared_statements",
      function( err, results ) {
        console.log( 'prepared statement count: '+results.rows[0].ct );
        client.query( {
                    name: 'test2' ,
                    text: "insert into t1( c2 ) values( 'q1')" },
          function( err, result ) {
            console.log( 'inserted t1' );
            client.query(
              "select count(1) as ct from pg_prepared_statements",
               function( err, results ) {
                  console.log( 'prepared statement count: '+results.rows[0].ct );
               } );
           }
        );
      }
    );
  }
);

if written procedurally would be

pg = new PG(...);
client = new pg.client();
console.log( client.col( "select ..." ) );
client.prepare( 'test2', "insert into t1( c2 ) values( 'q1')" );
console.log( client.col( "select ..." ) );

in my mind the latter is far more readable and maintainable.

is there some sort of compromise approach that would make the standard indented callback style more readable?

Answer 1

You want to use the async library’s waterfall mechanism:

var async = require('async');

async.waterfall([
    pg.connect.bind(this, {
        user: 'user', password: 'pass', port: 5432, host: '/somewhere/', database: 'db'
    }),
    function(client, callback) {
        client.query('select * from foo', callback)
    }
], function(err, results) {
    console.log(results);
});

The bind method added to Functions in ES5 is very useful in combination with the async library, since often the last argument in the list is a callback, and the earlier values are often known before entering the chain.