How to validate if input in input field exactly equals to some other value 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 some exact value and based on that we give the user access to the request or deny the request access. We can also validate these input fields to accept some exact required values otherwise deny the request 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 equals() with ‘ . ‘
- We can also use custom validator to validate if want to pass the required text to type in input field as a request body.
- 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 some exact value.
Filename – index.js
javascript
const express = require( 'express' )
const bodyParser = require( 'body-parser' )
const {validationResult} = require( 'express-validator' )
const repo = require( './repository' )
const { validateDeclaration } = require( './validator' )
const showTemplet = require( './show' )
const app = express()
const port = process.env.PORT || 3000
app.use(bodyParser.urlencoded({extended : true }))
app.get( '/' , (req, res) => {
res.send(showTemplet({}))
})
app.post(
'/record/delete/:id' ,
[validateDeclaration],
async (req, res) => {
const errors = validationResult(req)
if (!errors.isEmpty()){
return res.send(showTemplet({errors}))
}
const id = req.params.id
await repo. delete (id)
res.send( 'Record Deleted successfully' )
})
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
const fs = require( 'fs' )
class Repository {
constructor(filename) {
if (!filename){
throw new Error( 'Filename is required to create a datastore!' )
}
this .filename = filename
try {
fs.accessSync( this .filename)
} catch (err) {
fs.writeFileSync( this .filename, '[]' )
}
}
async getAll(){
return JSON.parse(
await fs.promises.readFile( this .filename, {
encoding : 'utf8'
})
)
}
async delete (id) {
const records = await this .getAll()
const filteredRecords = records.filter(record => record.id !== id)
await fs.promises.writeFile(
this .filename,
JSON.stringify(filteredRecords, null , 2)
)
}
}
module.exports = new Repository( 'datastore.json' )
|
Filename – show.js: This file contains logic to show declaration and input field to type declaration.
javascript
const getError = (errors, prop) => {
try {
return errors.mapped()[prop].msg
} catch (error) {
return ''
}
}
module.exports = ({errors}) => {
const id = 'd8f98678eb8a'
const declaration=
`I read all FAQ and wants to delete the record with id ${id}`
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' >
<div class= 'title is-5' >Declaration :</div>
<h2 class= 'subtitle is-5 has-text-danger' >
${declaration}
</h2>
<form action= 'record/delete/${id}' method= 'POST' >
<div>
<input type= 'text' hidden name= 'declaration'
value= '${declaration}' >
<input class= 'input' type= 'text'
name= 'typedDeclaration' placeholder
= 'Type Declaration' >
<p class="help is-danger">${getError(errors,
'typedDeclaration' )}</p>
</div>
<div>
<button class= 'button is-primary' >Delete</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 only allow some exact value).
javascript
const {check} = require( 'express-validator' )
const repo = require( './repository' )
module.exports = {
validateDeclaration : check( 'typedDeclaration' )
.trim()
.custom(async (typedDeclaration, {req}) => {
const declaration = req.body.declaration
if ( typedDeclaration !== declaration){
throw new Error( 'Please type exact declaration' )
}
})
}
|
Filename – package.json
package.json file
Database:
Database
Output:
Attempt to submit the form when input is not exactly equals to the declaration
Response when attempt to submit the form when input is not exactly equals to the declaration
Attempt to submit the form when input is exactly equals to the declaration
Response when attempt to submit the form when input is exactly equals to the declaration
Database after successful submission of form:
Database after successful submission of form
Note: We have used some Bulma classes(CSS framework) in the signup.js file to design the content.
Last Updated :
25 Jan, 2023
Like Article
Save Article
Share your thoughts in the comments
Please Login to comment...