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

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

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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 data
app.use(bodyParser.urlencoded({extended : true}))
  
// Get route to display HTML form
app.get('/', (req, res) => {
  res.send(formTemplet({}))
})
  
// Post route to handle form submission logic and 
app.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 setup
app.listen(port, () => {
  console.log(`Server start on port ${port}`)
})

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Filename – repository.js: This file contains all the logic to create a local database and interact with it.

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// Importing node.js file system module 
const 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 formet.
module.exports = new Repository('datastore.json')

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Filename – form.js: This file contains logic to show the form.

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const getError = (errors, prop) => {
  try {
    return errors.mapped()[prop].msg
  } catch (error) {
    return ''
  
}
  
module.exports = ({errors}) => {
  return `
    <!DOCTYPE html>
    <html>
      <head>
        <link rel='stylesheet' 
        <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>   
  `
}

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Filename – validator.js: This file contain all the validation logic(Logic to validate a input field to accept only a valid date).

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const {check} = require('express-validator')
const repo = require('./repository')
module.exports = {
    
  validateDOB : check('dob')
  
    // To delete leading and triling space
    .trim()
  
    // Validate DOB to be a valid date
    .isDate()
  
    // Custom message
    .withMessage('Must be a valid date')   
}

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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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