Jet-Validator

A super quick, easy to setup validation middleware function for ExpresssJS routes. Written in typescript ann fully typesafe :)

Quick start

• Call the jetValidator() function to return the validate() middleware function. If the validation fails, validate will return a 400 error with an error message. If you want to change the error status code, you can pass jetValidator() an optional parameter.

• Arguments to validate() must be a string or an array. If they're a string, validate() will make sure they are string on req.body.

• Note: json() and urlencoded() middleware must be added to express.

import express, { Request, Response } from 'express';
import jetValidator from 'jet-validator';

const app = express(),
  validate = jetValidator();

app.post(
  '/api/v1/login/local',
  validate('email', 'password'), // Will check that email and password are strings on req.body
  (req: Request, res: Response) => {
    const { email, password } = req.body;
    ...etc,
  },
);

Full guide

• As mentioned in the Quick Start, validate() accepts a string or an array.

• If a string, validate() makes sure the arguments is of type string on req.body.

• If the argument is an array the format is:

  [
    'paramName',
    '(optional) type or validator function (default is string)', 
    '(optional) property on "express.Request" to extract the value from (default is .body')
  ]

• For arrays, validate() makes sure the parameter is of the specified type or that the parameter satifies the validator function. The validator function must return true or false.

• Sample array1: ['id', 'number', 'body']. This will make sure id is of type number on req.body.

• Sample array2: ['email', isEmail]. This will make sure req.body.email satifies the isEmail function.

• Note for numbers on req.query and req.params: number-strings which pass !isNaN() are still valid. But on req.body a number should be typeof toCheck === "number".

• For booleans on req.query and req.params: boolean strings should be "true" or "false", but on req.body a boolean should typeof toCheck === "boolean".

More examples

• Example 1: validate('email', ['user', 'object'], ['id', 'number', 'params']) will check that email is a string in req.body, that user is of type object in req.body, and that id is a number in req.params.

• Example 2: validate('password') will check that password is a string on req.body.

• Example 3: validate(['isAdmin', 'boolean']) will check that isAdmin is a boolean on req.body.

• Example 4: validate(['user', isInstanceOfUser]) will check that req.body.user satifies the isInstanceOfUser() function.

• Example 5: validate(['email']) will check that email is a string in req.body.

• Example 6: validate(['id', 'number', 'params']) will check that id is a number-string in req.params.