Japper

Database library for PostgreSQL that doesn't get in your way but makes interacting with database more elegant.

It's a thin layer on top of node-postgres built with typescript in mind, heavily inspired by C# dapper library.

Writing raw SQL is the recommended way to do anything besides a couple goodies included like simple CRUD queries that are used always.

Be more productive when working with your database while still having all the control!

Documentation

Features

• Write plain SQL queries (no need to learn yet another "language" just to interact with a database)
• Generate INSERT/UPDATE queries based on object schema (making DTO classes single source of truth)
• Returns are key! Improve your code readability with getting the results back as needed (see examples below)
• Automatically open connection on first usage
• Everything great node-postgres already provides us with

Installation

$ npm install japper --save

Usage

All of the example are written with Typescript. Of course, this is usable without typescript, but I suggest you to try out Typescript :)

Usage with Express (connection pool example)

import { JapperPool } from "japper"; // import Japper Pool
import express from "express";
 
const app = express();
const PORT = 3000;
 
// create a Japper pool of connections
const db = new JapperPool({
  database: "db_name",
  user: "db_username",
  password: "db_password"
  // ....
});
 
class User {
  username!: string;
  email!: string;
};
 
app.get("/users", async (req, res) => {
  try {
    // execute SQL queries and get results back ready to be used
    res.status(200).send(await db.query<User>("SELECT * FROM users"));
  }
  catch(error) {
    ...
  }
});
 
app.listen(PORT, () => {
  console.log(`⚡️[server]: Server is running at https://localhost:${PORT}`)
});

Usage without a connection pool

import { JapperConnection } from "japper" // import Japper Connection
 
const config = {
  database: "db_name",
  user: "db_username",
  password: "db_password"
  // ....
};
 
class User {
  username!: string;
  email!: string;
};
 
try {
  const Users = new JapperConnection(config).open(async (cn) => {
    await cn.query<User>("SELECT * FROM users")
  }) // => Array<User>
  console.log(Users);
}
catch {
  ...
}

API documentation

Main usage

query - execute query and return array of found rows (preferably typed if using typescript)

async query<T extends object>(query: string, params?: any[] | undefined): Promise<T[]>

Example Usage:

const GmailUsers = await db.query<User>("SELECT * FROM users where email LIKE '%gmail.com'");
const PostsNewerThen = await db.query<Post>("SELECT * FROM posts where created_at >= $1", [new Date(2020, 1, 1)]);

queryFirst - execute query and return a single row as object (preferably typed if using typescript)

async queryFirst<T extends object>(query: string, params?: any[] | undefined): Promise<T | null>

Example Usage:

const FirstGmailUser = await db.queryFirst<User>("SELECT * FROM users where email LIKE '%gmail.com' ORDER BY ID ASC LIMIT 1");

executeScalar - execute query and return a single value as string

async executeScalar(query: string, params?: any[]): Promise<string | null>

Example Usage:

const FirstUserEmail = await db.executeScalar("SELECT email FROM users where id = $1", [1]);
const GetIDByUsername = parseInt(await db.executeScalar("SELECT id FROM users WHERE username = $1", ["someUsername"]));

execute - execute query and return number of changed rows

async execute(query: string, params?: any[]): Promise<number>

Example Usage:

const DeletedUsers = await db.execute("DELETE FROM users WHERE email LIKE '%gmail.com'");
console.log(`Deleted ${DeletedUsers} users`);

CRUD helpers

insert - insert row based on schema (making DTOs single source of truth)

async insert<T extends object, K extends keyof T>(tableName: string, obj: T, excludeFields: K[] | null = null): Promise<number>

Example Usage:

class User {
  id?: number;
  username!: string;
  password!: string;
}
 
await db.insert("users", { username: "test", password: "plainPasswordYuck" });
 
// or if we want to exclude some properties from inserting (in this example we don't insert id)
const newUser: User = { username: "test", password: "plainPasswordYuck" };
await db.insert("users", newUser, ["id"]);

insertReturning - insert row based on schema and return a field as string

async insertReturning<T extends object, R extends keyof T, E extends keyof T>(tableName: string, obj: T, returningPropertyName: R, excludeFields: E[] | null = null): Promise<string>

Example Usage:

// return id after inserting
const newUserID = await db.insertReturning("users", { username: "test", password: "plainPasswordYuck" }, "id");

update - update an object based on schema

async update<T extends object, K extends keyof T>(tableName: string, obj: T, primaryKeyName: K, excludeFields: K[] | null = null): Promise<number>

Example Usage:

// update user that has this id with this schema
const newUserID = await db.update("users", { id: 1, username: "changed", password: "plainPasswordYuck" }, "id");

delete - delete a row based on a single field

async delete(tableName: string, primaryKeyName: string = "id", primaryKeyValue: any): Promise<number>

Example Usage:

// delete user with id 1
const newUserID = await b.delete("users", "id", 1);

JapperPool vs JapperConnection

JapperPool maintains a pool of connections that can be reused. So when you create a new JapperPool you can just issue queries on it whenever you want. The pool can remain opened for ever. When you want to close the pool you call

.close()

JapperConnection is a one time connection that cannot be reused. So use them wisely! Connections should be opened as short as possible but opening and closing the connection is expensive so you could do multiple queries using one..be smart!

Example Usage:

import { JapperConnection } from "japper";
 
const config = {
  database: "db_name",
  user: "db_username",
  password: "db_password",
  // ....
};
 
//manually closing connection
const conn = new JapperConnection(config);
await conn.execute("DELETE FROM users"); // first query will automatically open connection
await conn.insert("users", { username: "test", email: "test" });
await conn.close(); //after we're done we close it
 
// if we need to use db again, we create a new connection again!
 
// better way (no need to manually close connection)
new JapperConnection(config)(async (cn) => {
  await cn.execute("DELETE FROM users");
  await cn.insert("users", { username: "test", email: "test" });
});

Accessing node-postgres

JapperConnection and JapperPoll have a property named adapter which is a node-postgres object!

Support

japper is free software. If you encounter a bug with the library please open an issue on the GitHub repo.

When you open an issue please provide:

• version of Node
• version of Postgres
• smallest possible snippet of code to reproduce the problem

Contributing

❤️ contributions!

I will happily accept your pull request if it:

• has tests
• added or changed functionality is in the japper philosophy
• does not break backwards compatibility

If your change involves breaking backwards compatibility please please point that out in the pull request & we can discuss & plan when and how to release it and what type of documentation or communication it will require.

Setting up for local development

1. Clone the repo
2. From your workspace root run yarn
3. Ensure you have a PostgreSQL instance running and an empty database for tests
4. Ensure you have the proper environment variables configured for connecting to the instance (see .sample-env and create .env file based on it)
5. Run yarn test to run all the tests

License

Copyright (c) 2020 Eric Jardas ([e-mail])

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.