How to validate if input date (end date) in input field must be after a given date (start 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 certain cases, we want the user to type a date that must come after some given date(Ex. ‘end date’ must be after ‘start date’) and based on that we give the user access to the request or deny the request access. We can also validate these input fields 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.
• Use custom validator to validate and fetch the start date as request body.
• Convert the date strings to a valid date and compare them according to requirement.
• 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 a input field to only allow a date after a given date.

Filename – index.js

Javascript

const express = require('express')
const bodyParser = require('body-parser')
const {validationResult} = require('express-validator')
const repo = require('./repository')
const { validateEndDate } = 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(
  '/project',
  [validateEndDate],
  async (req, res) => {
    const errors = validationResult(req)
    if (!errors.isEmpty()) {
      console.log(errors)
      return res.send(formTemplet({errors}))
    }

    const {name, domain, sdate, edate, } = req.body

    // Fetch year, month, day of respective dates
    const [sd, sm, sy] = sdate.split('/')
    const [ed, em, ey] = edate.split('/')

    // New record
    await repo.create({
      'Project Name': name,
      'Project Domain': domain,
      'Start Date': new Date(sy, sm-1, sd).toDateString(),
      'End Date': new Date(ey, em-1, ed).toDateString()
    })
 res.send('<strong>Project details stored '
    + 'successfully in the database</strong>')
})

// Server setup
app.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 module
const fs = require('fs')

class Repository {
  constructor(filename) {

    // Filename where data 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 to submit project data with start and end date.

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='/project' method='POST'>
                <div>
                  <div>
                    <label class='label' id='name'>Project Name</label>
                  </div>
                  <input class='input' type='text' name='name'
                  placeholder='Project Name' for='name'>
                </div>
                <div>
                  <div>
                    <label class='label' id='domain'>Project Domain</label>
                  </div>
                  <input class='input' type='text' name='domain'
                  placeholder='Project Domain' for='base64data'>
                </div>
                <div>
                  <div>
                    <label class='label' id='sdate'>Start Date</label>
                  </div>
                  <input class='input' type='text' name='sdate'
                  placeholder='dd/mm/yyyy' for='sdate'>
                </div>
                <div>
                  <div>
                    <label class='label' id='edate'>End Date</label>
                  </div>
                  <input class='input' type='text' name='edate'
                  placeholder='dd/mm/yyyy' for='edate'>
                  <p class="help is-danger">${getError(errors, 'edate')}</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 date after a given date).

Javascript

const {check} = require('express-validator')
const repo = require('./repository')
module.exports = {

  validateEndDate : check('edate')

    // To delete leading and trailing space
    .trim()

    // Custom validator
    .custom((edate, {req}) => {

      // Fetch year, month and day of respective dates
      const [sd, sm, sy] = req.body.sdate.split('/')
      const [ed, em, ey] = edate.split('/')

      // Constructing dates from given string date input
      const startDate = new Date(sy, sm, sd)
      const endDate = new Date(ey, em, ed)

      // Validate end date so that it must after start date
      if (endDate <= startDate) {
        throw new Error(
'End date of project must be after start date')
      }
      return true
    })
}

Filename – package.json

package.json file

Database:

Database

Output:

Attempt to submit form when end date comes before start date

Response when an attempt to submit the form where end date comes before start date

Attempt to submit form when end date comes after start date

Response when attempt to submit the form where end date comes after start 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.