FormValidator.js

function FormValidator(t, e) {
  this.form = t,
  this.errors = [],
  this.validators = [],
  $(this.form).on("submit", $.proxy(this, "onSubmit")),
  this.summary = e && e.summary ? $(e.summary) : $(".errorSummary"),
  this.summary.on("click", "a", $.proxy(this, "onErrorClick")),
  this.originalTitle = document.title
}
FormValidator.entityMap = {
  "&": "&",
  "<": "&lt;",
  ">": "&gt;",
  '"': "&quot;",
  "'": "&#39;",
  "/": "&#x2F;",
  "`": "&#x60;",
  "=": "&#x3D;"
},
FormValidator.escapeHtml = function(t) {
  return String(t).replace(/[&<>"'`=\/]/g, function(t) {
      return FormValidator.entityMap[t]
  })
}
,
FormValidator.prototype.onErrorClick = function(t) {
  t.preventDefault();
  var e = t.target.href
    , o = e.substring(e.indexOf("#"), e.length);
  $(o).focus()
}
,
FormValidator.prototype.resetTitle = function() {
  document.title = this.originalTitle
}
,
FormValidator.prototype.updateTitle = function() {
  document.title = "(" + this.errors.length + " errors) - " + document.title
}
,
FormValidator.prototype.showSummary = function() {
  this.summary.html(this.getSummaryHtml()),
  this.summary.removeClass("hidden"),
  this.summary.attr("aria-labelledby", "errorSummary-heading"),
  this.summary.focus()
}
,
FormValidator.prototype.getSummaryHtml = function() {
  var t = '<h2 class="h5 errorSummary-heading">There\'s a problem</h2>';
  t += "<ul>";
  for (var e = 0, o = this.errors.length; e < o; e++) {
      var i = this.errors[e];
      t += "<li>",
      t += '<a href="#' + FormValidator.escapeHtml(i.fieldName) + '">',
      t += FormValidator.escapeHtml(i.message),
      t += "</a>",
      t += "</li>"
  }
  return t += "</ul>"
}
,
FormValidator.prototype.hideSummary = function() {
  this.summary.addClass("hidden"),
  this.summary.removeAttr("aria-labelledby")
}
,
FormValidator.prototype.onSubmit = function(t) {
  this.removeInlineErrors();
  this.hideSummary();
  this.resetTitle();

  if (!this.validate()) {
    t.preventDefault();
    this.updateTitle();
    this.showSummary();
    this.showInlineErrors();
  }
}
,
FormValidator.prototype.showInlineErrors = function() {
  for (var t = 0, e = this.errors.length; t < e; t++)
      this.showInlineError(this.errors[t])
}
,

FormValidator.prototype.showInlineError = function(t) {
  var e = '<span class="field-error"> ' + FormValidator.escapeHtml(t.message) + "</span>"
    , o = $("#" + t.fieldName)
    , i = o.parents(".field")
    , n = i.find("label")
    , s = i.find("legend");
  i.find(".field-error").remove(),
  s.length ? (s.append(e),
  i.attr("aria-invalid", "true")) : (i.append(e),
  o.attr("aria-invalid", "true"))
}
,
FormValidator.prototype.removeInlineErrors = function() {
  $(this.form).find(".field-error").remove(),
  $(this.form).find("[aria-invalid]").attr("aria-invalid", "false")
}
,
FormValidator.prototype.addValidator = function(t, e) {
  this.validators.push({
      fieldName: t,
      rules: e,
      field: this.form.elements[t]
  })
}
,
FormValidator.prototype.validate = function() {
  this.errors = [];
  var t, e, o = null;
  for (t = 0; t < this.validators.length; t++)
      for (o = this.validators[t],
      e = 0; e < o.rules.length; e++)
          if (!o.rules[e].method(o.field, o.rules[e].params)) {
              this.errors.push({
                  fieldName: o.fieldName,
                  message: o.rules[e].message
              });
              break
          }
  return 0 === this.errors.length
}


var validator = new FormValidator(document.getElementById('registration'));
validator.addValidator("email", [
  {
    method: function (field) {
      return field.value.length > 0;
    },
    message: "Enter your email address",
  },
  {
    method: function (field) {
      return field.value.indexOf("@") > -1;
    },
    message: "You need to enter the ‘at’ symbol in the email address",
  },
]);
validator.addValidator("password", [
  {
    method: function (field) {
      return field.value.length > 0;
    },
    message: "Enter your password",
  },
  {
    method: function (field) {
      return field.value.length > 8;
    },
    message: "Your password must contain at least 8 characters",
  },
]);
validator.addValidator('personal-details', [
  {
    method: function (field) {
      return field.checked === true;
    },
    message: "You must waive your rights.",
  }
])