Question

Let’s say a user gets a page /form/

GET /form/

He then fills in the form and sends a post request

POST /form/

The server attempts to validate user input and determines input to be invalid.

Currently the history chain for the users is

• GET /form/
• POST /form/

Now the server redirects the user to the GET /form/ page so it can fill in the form again (with error messages).

His history looks like

• GET /form/ with filled in form fields
• GET /form/ without filed in form fields

How do I send the user back without the user losing the details he entered in his first form?

What techniques are there for redirecting users back to their GET /form/ page and not forcing them to re-enter their information.

Below is my express (node.js) specific server side code for this example.

The validation middleware:

validate().on("error", function _error(msg) {
    // store error message on request object
    req.flash(msg, validateUserMessage[msg]);
}).on("valid", function _valid() {
    // handle the rest of /POST/
    next();
}).on("invalid", function _invalid() {
    // redirect user back to last page, the /GET/ form
    res.redirect("back");
}).run(function _validateUsers(check, sanitize) {
    // validation logic.
}); 

The routing:

// GET /form/
app.get("/form", function _signUpView(req, res) {
    // render /form/
    res.render("auth/signup", req.flash());
});

// POST /form/
// validation middleware used here. 
app.post("/form", secure.validateUser, function _signUpCreate(req, res) {
    model.create(req.body, function _create() {
         // create thing in database
    });
});

Answer 1

I have decided to summarise the comments below into my answer:

To me, there seems to be only two sure ways of doing this:

1. Passing the user input parameters back from the server to the browser and repopulate the form either:

   a) Using a parameters object passed to the view and populating each field using your severside language

   b) Passing back a Json object and populating the form using loadJson

2. Using HTML5 local storage – which also requires JavaScript

If you do not persisit your data using either the server or JavaScript, then surely you are limiting yourself to relying on the browser – which is something you have no control over.

Good luck – if you do find a solution then please post it as your answer as I would be very intersted to see how you succeeded.