validating with expressjs inside (res, req) function instead of inside a middleware - express

Question

I'm using express-validator library to validate on the backend. This is the library:
https://express-validator.github.io/docs/index.html
I have this code
// ...rest of the initial code omitted for simplicity.
const { check, validationResult } = require('express-validator');
app.post('/user', [
check('username').isEmail(),
check('password').isLength({ min: 5 })
], (req, res) => {
// Finds the validation errors in this request and wraps them in an object with handy functions
const errors = validationResult(req);
if (!errors.isEmpty()) {
return res.status(422).json({ errors: errors.array() });
}
User.create({
username: req.body.username,
password: req.body.password
}).then(user => res.json(user));
});
Is it possible to call validation function inside the (req, res) =>{ }
I have some requirements where I need to check what has arrived in via request before I can construct the validation array.
Basically I would like to be able to do this:
app.post('/user', (req, res) => {
const { importantParam, email, password, firstname, lastname } = request.body
let validateThis = []
if(importantParam == true)
validateThis = [
check('username').isEmail(),
check('password').isLength({ min: 5 })
]
else
validateThis = [
check('username').isEmail(),
check('password').isLength({ min: 5 })
check('firstname').isLength({ min: 5 })
check('lastname').isLength({ min: 5 })
]
runValidationFunction(validateThis)
//now below code can check for validation errors
const errors = validationResult(req);
if (!errors.isEmpty()) {
return res.status(422).json({ errors: errors.array() });
}
User.create({
username: req.body.username,
password: req.body.password
}).then(user => res.json(user));
});
This is what I need to do, construct the validation array based on if one of the params has a specific value. I can't figure out how to do that with the first example since it seems request is not possible to access when taking this approach
app.post('/user', validationArray, (req, res) => {}
Any ideas how I can call express-validate validate function directly inside
(req, res) => {}

Answer 1

What you can do is to run a check inside a custom validation. You should require validator as well.
const { check, body, param } = require('express-validator/check');
const { validator } = require('express-validator');
const checkValidation = () => {
return [
check('importantParam')
.custom((value, {req}) => {
const data = req.body;
if (!validator.isEmail(data.username)) throw new Error("Not valid Email");
if (!validator.isLength(data.password, {min:5})) throw new Error("Not valid password");
// if importantParam is false, add the following properties to validation
if (!value) {
if (!validator.isLength(data.firstname, {min:5})) throw new Error("Not valid firstname");
if (!validator.isLength(data.lastname, {min:5})) throw new Error("Not valid lastname");
}
return true;
})
];
};
app.post('/user', checkValidation(), (req, res) => {
//now below code can check for validation errors
const errors = validationResult(req);
if (!errors.isEmpty()) {
return res.status(422).json({ errors: errors.array() });
}
// do stuff here
});
Hope it helps!