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3.2.0 • Public • Published

krauter version

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krauter allows you to quickly create data-backed web services by configuring an Express router with a database connection and automatically producing parameterized query middleware from strings and objects. Middleware can also be produced from integers (sets the HTTP response status code), unary functions (sets the value of req.data), and null (clears the value of req.data).

It currently supports hassle-free integration with PostgreSQL (pg), MySQL (mysql), SQL Server (mssql), and SQLite (sqlite3).


npm install --save krauter

And depending on which DBMS is being used:

npm install --save pg
npm install --save mysql
npm install --save mssql
npm install --save sqlite3


Each Krauter must be created with a supplied executor function that simply takes a query along with an array of parameter values (and optionally an array of corresponding datatypes) and returns a promise for the results. krauter has predefined executors available for supported DBMSs. These can be used by calling krauter.DBMS(connection[, options]) (where DBMS is the name of a supported DBMS's npm package) with a corresponding connection/pool and an options object (used for the Express router), which will return a Krauter configured to run queries on that specific connection/pool.

const krauter = require('krauter');
const mysql = require('mysql');
// Create database connection pool
const pool = mysql.createPool({
    host: process.env.DB_HOST,
    user: process.env.DB_USER,
    password: process.env.DB_PASSWORD,
    database: process.env.DB_NAME
// Create a Krauter
const api = krauter.mysql(pool);

A Krauter can also be initialized with a custom executor function:

const api = krauter((query, values) => new Promise((resolve, reject) => { /* ... */ }));


A Krauter works the same as a normal Express router, but with the added capability of its HTTP methods (including all) taking various argument types and internally replacing them with middleware.


When a string is encountered, it is replaced with a middleware function that will execute the string as a query to the configured database and then store the result to req.data.

api.get('/products', 'SELECT * FROM products');

When an object is encountered, each of its properties' values will be interpreted as a query (to be ran in parallel) with each result being stored as a property of req.data (with the same key).

api.get('/filters', {categories: 'SELECT id, name FROM categories', merchants: 'SELECT id, name FROM merchants'});

JavaScript values can be specified within query strings and they will automatically be inserted to form a parameterized query (preventing SQL injection). Values may be any recursive property of the req object and are denoted in dot notation within surrounding colons.

Note: The res object can be accessed with req.res

api.get('/merchants/:id', 'SELECT * FROM merchants WHERE id = :params.id:');

For DBMSs that typically have datatypes specified for parameters (such as mssql), the datatype can be denoted within surrounding braces preceding the specified property.

    'INSERT INTO products (merchantId, name, price)' +
    'VALUES (:{Int}user.id:, :{VarChar(45)}body.name:, :{Money}body.price:)');

Transformations of req.data

When a unary function is encountered, it is replaced with a middleware function that will call it with the supplied argument being a single object containing properties req, res, and data, where the value of data is taken (and removed) from req.data. The value returned from the unary function is then subsequently set to req.data (unless a Query object is returned... see below).

A unary function can be defined in a syntactically similar manner as a typical middleware function by using destructuring assignments and unpacking them from the single object argument.

    'SELECT * FROM orders WHERE id = :params.id:',
    ({req, res, data: [{confirmedUtc, ... order}]}) =>
        ({confirmedLocal: new Date(confirmedUtc).toLocaleString(req.user.language, {timeZone: req.user.timeZone}), ... order}));
Returning another Query

krauter exposes a Query global constructor that can be used to return a value from within a unary function which will be processed just like a normal Krauter HTTP method argument. You can think of it as like returning a Promise from within a Promise.prototype.then() handler... a unary function that returns a Query will instead return the result from executing the Query. This allows for the building of more dynamic queries which would otherwise be very difficult to create using only variable expansion.

Clearing req.data

When null is encountered, it is replaced with a middleware function that removes the value of req.data.

HTTP Response Status Codes

When a number is encountered, it is replaced with a middleware function that will set it as the response's status code.

    'INSERT INTO reviews (productId, userId, rating, message)' +
    'VALUES (:params.productId:, :params.userId:, :body.rating:, :body.message:)',

Automatic Responses

Each Krauter automatically sends a response with req.data as the body if the request previously matched a route but has not been answered. This can be bypassed singularly by calling next('router') within a middleware function, or completely by setting the automatic option to false when constructing your Krauter.

const api = krauter(executor, {automatic: false});


Clone the repo locally, and then:

npm install
npm test


Check out the issues page or make a pull request to contribute!


npm i krauter

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