/my-cartridge
    /cartridge
        /forms
            /default              # Default locale
                profile.xml
                contact.xml
            /de_DE               # German-specific (optional)
                address.xml

<?xml version="1.0" encoding="UTF-8"?>
<form xmlns="http://www.demandware.com/xml/form/2008-04-19">
    <field formid="email" label="form.email.label" type="string"
           mandatory="true" max-length="50"
           regexp="^[\w.%+-]+@[\w.-]+\.\w{2,6}$"
           parse-error="form.email.invalid"/>

    <field formid="password" label="form.password.label" type="string"
           mandatory="true" min-length="8" max-length="255"
           missing-error="form.password.required"/>

    <field formid="rememberMe" label="form.remember.label" type="boolean"/>

    <action formid="submit" valid-form="true"/>
    <action formid="cancel" valid-form="false"/>
</form>

'use strict';

var server = require('server');
var csrfProtection = require('*/cartridge/scripts/middleware/csrf');

server.get('Show',
    csrfProtection.generateToken,
    function (req, res, next) {
        var form = server.forms.getForm('profile');
        form.clear();  // Reset previous values

        res.render('account/profile', {
            profileForm: form
        });
        next();
    }
);

module.exports = server.exports();

server.post('Submit',
    server.middleware.https,
    csrfProtection.validateAjaxRequest,
    function (req, res, next) {
        var form = server.forms.getForm('profile');

        if (!form.valid) {
            res.json({
                success: false,
                fields: getFormErrors(form)
            });
            return next();
        }

        // Access form values
        var email = form.email.value;
        var firstName = form.firstName.value;

        // Process and save data
        this.on('route:BeforeComplete', function () {
            var Transaction = require('dw/system/Transaction');
            Transaction.wrap(function () {
                customer.profile.email = email;
                customer.profile.firstName = firstName;
            });
        });

        res.json({ success: true });
        next();
    }
);

function getFormErrors(form) {
    var errors = {};
    Object.keys(form).forEach(function (key) {
        if (form[key] && form[key].error) {
            errors[key] = form[key].error;
        }
    });
    return errors;
}

server.get('Edit', function (req, res, next) {
    var form = server.forms.getForm('profile');
    form.clear();

    var profile = req.currentCustomer.profile;
    form.firstName.value = profile.firstName;
    form.lastName.value = profile.lastName;
    form.email.value = profile.email;

    res.render('account/editProfile', { profileForm: form });
    next();
});

<form action="${pdict.actionUrl}" method="POST" name="profile-form"
      class="form-horizontal" data-action="${URLUtils.url('Profile-Submit')}">

    <!-- CSRF Token -->
    <input type="hidden" name="${pdict.csrf.tokenName}" value="${pdict.csrf.token}"/>

    <div class="form-group ${pdict.profileForm.email.mandatory ? 'required' : ''}">
        <label for="email" class="form-control-label">
            ${Resource.msg('form.email.label', 'forms', null)}
        </label>
        <input type="email"
               id="email"
               name="email"
               class="form-control ${pdict.profileForm.email.error ? 'is-invalid' : ''}"
               value="${pdict.profileForm.email.value || ''}"
               <isif condition="${pdict.profileForm.email.mandatory}">required</isif>
               maxlength="${pdict.profileForm.email.maxLength || 50}"/>
        <isif condition="${pdict.profileForm.email.error}">
            <div class="invalid-feedback">${pdict.profileForm.email.error}</div>
        </isif>
    </div>

    <button type="submit" class="btn btn-primary">
        ${Resource.msg('button.submit', 'forms', null)}
    </button>
</form>

form.email.label=Email Address
form.email.required=Email is required
form.email.invalid=Please enter a valid email address
form.password.label=Password
button.submit=Submit

form.email.label=E-Mail-Adresse
form.email.required=E-Mail ist erforderlich