Is there a standard way to do backend validation?

Question

I'm writing a simple CRUD application in express.js and node.js and while developing the backend APIs this is what I came up with

app.post("/signup", (req, res) => {
  const { name, email, password } = req.body;
  if (!name) {
    res.status(401).json("Please provide a name.");
  } else if (!email) {
    res.status(401).json("Please provide an email.");
  } else if (!password) {
    res.status(401).json("Please provide a password.");
  }
});

Is there a better way to do this? I want to make sure that even if the frontend required HTML input fields are bypassed, the data is still validated in the backend.

Answer 1

I'd recommend combining them into a single response. Otherwise the user may correct one error only to be presented with another, and wondering why both errors weren't shown in the first place.

Maybe something like:

app.post("/signup", (req, res) => {
  const { name, email, password } = req.body;

  const errs = [];
  if (!name) {
    errs.push("Please provide a name.");
  }
  if (!email) {
    errs.push("Please provide an email.");
  }
  if (!password) {
    errs.push("Please provide a password.");
  }

  if (errs.length > 0) {
    res.status(401).json(errs);
  } else {
    // handle success here
  }
});