ngPattern adds the pattern validator to ngModel. It is most often used for text-based input controls, but can also be applied to custom text-based controls.

The validator sets the pattern error key if the ngModel.$viewValue does not match a RegExp which is obtained by evaluating the Angular expression given in the ngPattern attribute value:

If the expression evaluates to a RegExp object, then this is used directly.
If the expression evaluates to a string, then it will be converted to a RegExp after wrapping it in ^ and $ characters. For instance, "abc" will be converted to new RegExp('^abc$').

Note: Avoid using the g flag on the RegExp, as it will cause each successive search to start at the index of the last search's match, thus not taking the whole input value into account.

Note: This directive is also added when the plain pattern attribute is used, with two differences:

ngPattern does not set the pattern attribute and therefore HTML5 constraint validation is not available.
The ngPattern attribute must be an expression, while the pattern value must be interpolated.

Directive Info

This directive executes at priority level 0.

Usage

as attribute:
```
<ANY>
...
</ANY>
```

Example

Edit in Plunker

<script>
  angular.module('ngPatternExample', [])
    .controller('ExampleController', ['$scope', function($scope) {
      $scope.regex = '\\d+';
    }]);
</script>
<div ng-controller="ExampleController">
  <form name="form">
    <label for="regex">Set a pattern (regex string): </label>
    <input type="text" ng-model="regex" id="regex" />
    <br>
    <label for="input">This input is restricted by the current pattern: </label>
    <input type="text" ng-model="model" id="input" name="input" ng-pattern="regex" /><br>
    <hr>
    input valid? = <code>{{form.input.$valid}}</code><br>
    model = <code>{{model}}</code>
  </form>
</div>

var model = element(by.binding('model'));
var input = element(by.id('input'));

it('should validate the input with the default pattern', function() {
  input.sendKeys('aaa');
  expect(model.getText()).not.toContain('aaa');

  input.clear().then(function() {
    input.sendKeys('123');
    expect(model.getText()).toContain('123');
  });
});