Nick's solution

validator.js

@@ -1,7 +1,53 @@
+// jQuery elements
+var $email = $('form input[type=text]');
+var $password = $('form input[type=password]');
+var $submit = $('form input[type=submit]');
+var $errors = $('.errors li');
 
-  //insert your code here
-
-$(function(){
+// Form validators, matching to each of the four errors in order
+var validators = [
+  // Please enter a valid email address
+  function () {
+    return /^.+@.+\..+$/.test($email.val());
+  },
 
-  //insert your code here
+  // Your password should be at least 8 characters long
+  function () {
+    return $password.val().length >= 8;
+  },
+
+  // Your password should contain at least one capital letter
+  function () {
+    return /[A-Z]/.test($password.val());
+  },
+
+  // Your password should contain at least one number (0-9)
+  function () {
+    return /\d/.test($password.val());
+  }
+];
+
+// Hides all validation errors
+function hideErrors() {
+  $errors.hide();
+  $submit.prop('disabled', false);
+}
+
+// Runs all validators and display any errors that occur
+function validate() {
+  hideErrors();
+  validators.forEach(function (validator, index) {
+    if (!validator()) {
+      $errors.eq(index).show();
+      $submit.prop('disabled', true);
+    }
+  });
+}
+
+// Run validators initially and whenever an input is updated
+$(function () {
+  hideErrors();
+  validate();
+  $email.on('keyup', validate);
+  $password.on('keyup', validate);
 });