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2.0.2 • Public • Published


NPM version

DDL.js is a library that queries database and table schemas (currently from PostgreSQL and SQLite3) and describes their columns with JSON Schema v4.

You can use DDL.js for introspection, to prepare your domain models and set up simple type coercions or validations for those database columns. This way you can have the same convenience that Ruby on Rails's ActiveRecord provides, but in the JavaScript world.

DDL.js is open for extension and modifications, so if you have suggestions what more it should define or query from the database, please ping me with an email, a tweet or create an issue on GitHub.


npm install ddl

DDL.js follows semantic versioning, so feel free to depend on its major version with something like >= 1.0.0 < 2 (a.k.a ^1.0.0).


Each database has its own function you can call passing it the connection to that database and the table name you'd like to get a data definition for. Look at DDL.js API Documentation for a list of supported databases.

Given the following table:

CREATE TABLE "golfers" (
  "name" VARCHAR(255) DEFAULT 'Tiger' NOT NULL,
  "updated_at" DATETIME

And the following code:

var Pg = require("pg")
var db = new Pg.Client
db.connect({database: "golf"})
var Ddl = require("ddl")
Ddl.postgresql(db, "golfers", function(err, ddl) {})

Your callback will be called with the following object for ddl:

  name: {type: "string", default: "Tiger", maxLength: 255},
  handicap: {type: "integer", default: 52},
  updated_at: {type: ["string", "null"], default: null}

This works well if you have a single JavaScript "class" or model per database table. With DDL.js you can initialize that model's attributes and their default values without having to manually keep the database and the model declaration in sync.

If you want to use the returned definition with a JSON Schema validator library, use it like this:

var Jsck = require("jsck")
var ddl = Ddl.postgresqlSync(db, "golfers")
var validation = new Jsck.draft4({type: "object", properties: ddl})
validation.validate({name: "John", handicap: 13})


For extended documentation on all functions, please see the DDL.js API Documentation.




DDL.js is released under a Lesser GNU Affero General Public License, which in summary means:

  • You can use this program for no cost.
  • You can use this program for both personal and commercial reasons.
  • You do not have to share your own program's code which uses this program.
  • You have to share modifications (e.g bug-fixes) you've made to this program.

For more convoluted language, see the LICENSE file.


Andri Möll typed this and the code.
Monday Calendar supported the engineering work.

If you find DDL.js needs improving, please don't hesitate to type to me now at or create an issue online.


npm i ddl

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