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                <form action="" x-data="form" @focusout="change" @input="change" @submit="submit">

  <label for="username">Username</label>
  <input name="username" id="username" type="text" x-bind:class="{'invalid':username.errorMessage}" data-rules='["required"]' data-server-errors='[]'>
  <p class="error-message" x-show="username.errorMessage" x-text="username.errorMessage" x-transition:enter></p>

  <label for="email">Email</label>
  <input name="email" type="email" id="email" x-bind:class="{'invalid':email.errorMessage}" data-rules='["required","email"]' data-server-errors='[]'>
  <p class="error-message" x-show="email.errorMessage" x-text="email.errorMessage" x-transition:enter></p>

  <label for="password">Password</label>
  <input name="password" type="password" id="password" x-bind:class="{'invalid':password.errorMessage}" data-rules='["required","minLength:8"]' data-server-errors='[]'>
  <p class="error-message" x-show="password.errorMessage" x-text="password.errorMessage" x-transition:enter></p>

  <label for="passwordConf">Confirm Password</label>
  <input name="passwordConf" type="password" id="passwordConf" x-bind:class="{'invalid': passwordConf.errorMessage}" data-rules='["required","minLength:8","matchingPassword"]' data-server-errors='[]'>
  <p class="error-message" x-show="passwordConf.errorMessage" x-text="passwordConf.errorMessage" x-transition:enter></p>

  <input type="submit">


                * {
  font-family: "Inter", sans-serif;
form {
  width: 40%;
  min-width: 450px;
  margin: auto;
label {
  font-size: 1.5em;

input {
  width: 100%;
  display: block;
  font-size: 2em;
  border: solid 4px;
  border-color: hsl(210, 100%, 30%);
  margin-bottom: 1.5em;
input[type="submit"] {
  width: fit-content;
  font-size: 1.5em;

input[type="submit"]:focus {
  background-color: hsl(210, 100%, 80%);
input[type="submit"]:active {
  background-color: hsl(200, 100%, 80%);
.invalid {
  border-color: darkred;
  background-color: hsl(0, 30%, 95%);
  margin-bottom: 0em;
.error-message {
  margin-bottom: 1em;
  color: hsl(0deg, 100%, 15%);



                import Alpine from "";
import kingshottIodine from "";"form", form);

function form() {
  return {
    inputElements: [],
    init() {
      //Set up custom Iodine rules
        (value) => value === document.getElementById("password").value
        "Password confirmation needs to match password"
      //Store an array of all the input elements with 'data-rules' attributes
      this.inputElements = [...this.$el.querySelectorAll("input[data-rules]")];
    initDomData: function () {
      //Create an object attached to the component state for each input element to store its state => {
        this[] = {
          serverErrors: JSON.parse(ele.dataset.serverErrors),
          blurred: false
    updateErrorMessages: function () {
      //map throught the input elements and set the 'errorMessage' => {
        this[].errorMessage = this.getErrorMessage(ele);
    getErrorMessage: function (ele) {
      //Return any server errors if they're present
      if (this[].serverErrors.length > 0) {
        return input.serverErrors[0];
      //Check using iodine and return the error message only if the element has not been blurred
      const error = Iodine.assert(ele.value, JSON.parse(ele.dataset.rules));
      if (!error.valid && this[].blurred) {
        return error.error;
      //return empty string if there are no errors
      return "";
    submit: function (event) {
      const invalidElements = this.inputElements.filter((input) => {
        return (
          Iodine.assert(input.value, JSON.parse(input.dataset.rules)) !== true
      if (invalidElements.length > 0) {
        //We set all the inputs as blurred if the form has been submitted => {
          this[].blurred = true;
        //And update the error messages.
    change: function (event) {
      //Ignore all events that aren't coming from the inputs we're watching
      if (!this[]) {
        return false;
      if (event.type === "input") {
        this[].serverErrors = [];
      if (event.type === "focusout") {
        this[].blurred = true;
      //Whether blurred or on input, we update the error messages