validate.js

/**
 * General-purpose validator for ngModel.
 * angular.js comes with several built-in validation mechanism for input fields (ngRequired, ngPattern etc.) but using
 * an arbitrary validation function requires creation of a custom formatters and / or parsers.
 * The ui-validate directive makes it easy to use any function(s) defined in scope as a validator function(s).
 * A validator function will trigger validation on both model and input changes.
 *
 * @example <input ui-validate="myValidatorFunction">
 * @example <input ui-validate="{foo : validateFoo, bar : validateBar}">
 *
 * @param ui-validate {string|object literal} If strings is passed it should be a scope's function to be used as a validator.
 * If an object literal is passed a key denotes a validation error key while a value should be a validator function.
 * In both cases validator function should take a value to validate as its argument and should return true/false indicating a validation result.
 */
angular.module('ui.directives').directive('uiValidate', function () {

  return {
    restrict: 'A',
    require: 'ngModel',
    link: function (scope, elm, attrs, ctrl) {
      var validateFn, validateExpr = attrs.uiValidate;

      validateExpr = scope.$eval(validateExpr);
      if (!validateExpr) {
        console.log('WHASd');
        return;
      }

      if (angular.isFunction(validateExpr)) {
        validateExpr = { validator: validateExpr };
      }

      angular.forEach(validateExpr, function (validatorFn, key) {
        validateFn = function (valueToValidate) {
          if (validatorFn(valueToValidate)) {
            ctrl.$setValidity(key, true);
            return valueToValidate;
          } else {
            ctrl.$setValidity(key, false);
            return undefined;
          }
        };
        ctrl.$formatters.push(validateFn);
        ctrl.$parsers.push(validateFn);
      });
    }
  };
});