array passed as argument to express post method

Question

I'm currently learning express-validator, in the docs there is an example like:

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

app.post('/user', [
  // username must be an email
  check('username').isEmail(),
  // password must be at least 5 chars long
  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));
});

So, I don't understand why is ther an array passed to the post method. And, can you tell me how can I learn more about it?

Thank you in advance.

Answer 1

As you can read in expressjs docs, passing array is the same as passing multiple arguments. This has been done to enable reuse of multiple middlewares.