Trim input values before express-validator in Node.Js

I'm using the suggested V4 syntax of express-validator in a Node.js project:

const { check, validationResult } = require('express-validator/check');
const { matchedData } = require('express-validator/filter');

and

app.post('/users/add/',[
check('first_name')
.isLength({ min: 1 }).withMessage('A first name is required')],
(req, res, next) => {
  var errors = validationResult(req);
  if (errors) {
     ..etc

Note that I am using the modern syntax and do not have the following code (as per the express-validator README.md file):

const expressValidator = require('express-validator');
app.use(expressValidator());

How do I trim blank spaces from the input field before running the validation?

Answers:

Answer

You should use .trim() before your .check() like this,

check('first_name').trim().isLength({ min: 1 }).withMessage('A first name is required')]

Hope this helps!

Answer

The following work around may help, though I think the best solution would be to support sanitation in a fluent manner. The downside of my work around is that the processing of input is now in two places.

  1. Add the required sanitation functions to requires clause:

    const { trim } = require('express-validator').validator
    
  2. Adjust the request processing:

    app.post('/users/add/',
     (req, res, next) => {
    req.body.first_name = trim(req.body.first_name);
    req.body.last_name = trim(req.body.last_name);
    req.body.email = trim(req.body.email);
    next();
    },
    [check('first_name')
    .isLength({ min: 1 }).withMessage('A first name is required')],
    (req, res, next) => {
     var errors = validationResult(req);
     if (errors) {
    ..etc
    

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