Handy JS regex validation functions for email, name and website fields.

validateEmail.js

// Source: https://stackoverflow.com/questions/46155/how-to-validate-an-email-address-in-javascript
function validateEmail(id) {
  var regex = /^(([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/i;
	var ctrl = document.getElementById(id);

	if (regex.test(ctrl.value)) {
		return true;
	}
	else {
		return false;
	}
}

validateName.js

// Source: https://stackoverflow.com/questions/20690499/concrete-javascript-regex-for-accented-characters-diacritics
function validateName(id) {
  var regex = /^[a-zA-Z\u00C0-\u024F\u1E00-\u1EFF]{3,50}$/;
  var ctrl = document.getElementById(id);

  if (regex.test(ctrl.value)) {
    return true;
  }
  else {
    return false;
  }
}

validateWebsite.js

// Source: https://stackoverflow.com/questions/3809401/what-is-a-good-regular-expression-to-match-a-url
function validateWebsite(id) {
	var regex = /(https?:\/\/(?:www\.|(?!www))[a-zA-Z0-9][a-zA-Z0-9-]+[a-zA-Z0-9]\.[^\s]{2,}|www\.[a-zA-Z0-9][a-zA-Z0-9-]+[a-zA-Z0-9]\.[^\s]{2,}|https?:\/\/(?:www\.|(?!www))[a-zA-Z0-9]+\.[^\s]{2,}|www\.[a-zA-Z0-9]+\.[^\s]{2,})/;
	var ctrl = document.getElementById(id);
        // To allow if empty: if (regex.test(ctrl.value) || ctrl.value === "")
	if (regex.test(ctrl.value)) {
		return true;
	}
	else {
		return false;
	}
}