How to validate if input in input field is a valid date using express-validator ?

08 Apr, 2022
In HTML forms, we often required validation of different types. Validate existing email, validate password length, validate confirm password, validate to allow only integer inputs, these are some examples of validation. In a certain input field, only a valid date is allowed i.e. there is not allowed any strings, number, or invalid date characters. We can also validate these input fields to accept only a valid date using express-validator middleware.
Command to install express-validator:
npm install express-validator
Steps to use express-validator to implement the logic:
Install express-validator middleware.
Create a validator.js file to code all the validation logic.
Validate input by validateInputField: check(input field name) and chain on the validation isDate() with ‘ . ‘
Use the validation name(validateInputField) in the routes as a middleware as an array of validations.
Destructure ‘validationResult’ function from express-validator to use it to find any errors.
If error occurs redirect to the same page passing the error information.
If error list is empty, give access to the user for the subsequent request.
Note: Here we use local or custom database to implement the logic, the same steps can be followed to implement the logic in a regular database like MongoDB or MySql.
Example: This example illustrates how to validate an input field to accept only a valid date.
Filename – index.js
javascript
const express = require('express')const bodyParser = require('body-parser')const {validationResult} = require('express-validator')const repo = require('./repository')const { validateDOB } = require('./validator')const formTemplet = require('./form') const app = express()const port = process.env.PORT || 3000 // The body-parser middleware to parse form dataapp.use(bodyParser.urlencoded({extended : true})) // Get route to display HTML formapp.get('/', (req, res) => {  res.send(formTemplet({}))}) // Post route to handle form submission logic andapp.post(  '/info',  [validateDOB],  async (req, res) => {    const errors = validationResult(req)    if (!errors.isEmpty()) {      return res.send(formTemplet({errors}))    }     const {email, name, phn, dob} = req.body     // New record    await repo.create({      email,      name,      'phone number':phn,      'Date of Birth':dob    })res.send('<strong>Information is saved to '   + 'the database successfully</strong>')}) // Server setupapp.listen(port, () => {  console.log(`Server start on port ${port}`)})
Filename – repository.js: This file contains all the logic to create a local database and interact with it.
javascript
// Importing node.js file system moduleconst fs = require('fs') class Repository {     constructor(filename) {         // Filename where datas are going to store        if (!filename) {            throw new Error('Filename is required to create a datastore!')        }         this.filename = filename         try {            fs.accessSync(this.filename)        } catch (err) {             // If file not exist it is created            // with empty array            fs.writeFileSync(this.filename, '[]')        }    }     // Get all existing records    async getAll() {        return JSON.parse(            await fs.promises.readFile(this.filename, {                encoding: 'utf8'            })        )    }     // Create new record    async create(attrs) {        // Fetch all existing records        const records = await this.getAll()         // All the existing records with new        // record push back to database        records.push(attrs)        await fs.promises.writeFile(            this.filename,            JSON.stringify(records, null, 2)        )        return attrs    }} // The 'datastore.json' file created at runtime// and all the information provided via signup form// store in this file in JSON format.module.exports = new Repository('datastore.json')
Filename – form.js: This file contains logic to show the form.
javascript
const getError = (errors, prop) => {  try {    return errors.mapped()[prop].msg  } catch (error) {    return ''  }} module.exports = ({errors}) => {  return `    <!DOCTYPE html>    <html>      <head>        <link rel='stylesheet'href='https://cdnjs.cloudflare.com/ajax/libs/bulma/0.9.0/css/bulma.min.css'>        <style>          div.columns{            margin-top: 100px;          }          .button{            margin-top : 10px          }        </style>      </head>      <body>        <div class='container'>          <div class='columns is-centered'>            <div class='column is-5'>              <form action='/info' method='POST'>                <div>                  <div>                    <label class='label' id='email'>Email</label>                  </div>                  <input class='input' type='text' name='email'                  placeholder='Email' for='email'>                </div>                         <div>                  <div>                    <label class='label' id='name'>Name</label>                  </div>                  <input class='input' type='text' name='name'                  placeholder='Name' for='name'>                </div>                <div>                  <div>                    <label class='label' id='phn'>Phone Number</label>                  </div>                  <input class='input' type='text' name='phn'                  placeholder='Phone Number' for='phn'>                </div>                <div>                  <div>                    <label class='label' id='dob'>Date Of Birth</label>                  </div>                  <input class='input' type='date' name='dob'                  placeholder='DOB' for='dob'>                  <p class="help is-danger">${getError(errors, 'dob')}</p>                </div>                <div>                  <button class='button is-primary'>Submit</button>                </div>              </form>            </div>          </div>        </div>      </body>    </html>    `}
Filename – validator.js: This file contain all the validation logic(Logic to validate a input field to accept only a valid date).
javascript
const {check} = require('express-validator')const repo = require('./repository')module.exports = {     validateDOB : check('dob')     // To delete leading and trailing space    .trim()     // Validate DOB to be a valid date    .isDate()     // Custom message    .withMessage('Must be a valid date')  }
Filename – package.json
Package.json file
Database:
Database
Output:
Attempt to submit form when DOB input field has invalid date
Response when attempt to submit form where DOB input field has invalid date
Attempt to submit form when DOB input field has valid date
Response when attempt to submit form where DOB input field has valid date
Database after successful form submission:
Database after successful submission of form
Note: We have used some Bulma classes(CSS framework) in the signup.js file to design the content.
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Express.js
Node.js-Misc
Node.js
Web Technologies
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