How to detect input element change when set value in angularjs

Question

online code:

http://jsfiddle.net/mb98y/309/

HTML

<div ng-app="myDirective" ng-controller="x">
    <input id="angular" type="text" ng-model="data.test" my-directive>
</div>
    <button onclick="document.querySelector('#angular').value = 'testg';">click</button>

JS

angular.module('myDirective', [])
    .directive('myDirective', function () {
    return {
        restrict: 'A',
        link: function (scope, element, attrs) {
            scope.$watch(attrs.ngModel, function (v) {
                //console.log('value changed, new value is: ' + v);
                alert('value change: ' + scope.data.test);
            });
        }
    };
});

function x($scope) {
    //$scope.test = 'value here';
    $scope.data = {
        test: 'value here'
    }
}

http://jsfiddle.net/mb98y/310/

HTML

<div ng-app="myDirective" ng-controller="x">
<input id="angular" type="text" my-directive="test">{{test}}</div>
<button onclick="document.querySelector('#angular').value =  'testg';">click</button>

JS

angular.module('myDirective', [])
    .directive('myDirective', function () {
    return {
        restrict: 'A',
        scope: {
            myDirective: '='
        },
        link: function (scope, element, attrs) {
            // set the initial value of the textbox
            element.val(scope.myDirective);
            element.data('old-value', scope.myDirective);

            // detect outside changes and update our input
            scope.$watch('myDirective', function (val) {
                element.val(scope.myDirective);
            });

            // on blur, update the value in scope
            element.bind('propertychange keyup change paste', function (blurEvent) {
                if (element.data('old-value') != element.val()) {
                    console.log('value changed, new value is: ' + element.val());
                    scope.$apply(function () {
                        scope.myDirective = element.val();
                        element.data('old-value', element.val());
                    });
                }
            });
        }
    };
});

function x($scope) {
    $scope.test = 'value here';
}

I wanna click button to set input element value and angularjs(ng-model or scope object) can get it.

But, document.querySelector('#angular').value = 'testg';

change element value in this way, Neither angularjs $watch nor bind function can get value change event. If you input some words in input element by keyboard, they both works.

How can I detect input element value change when set value in this way in angularjs?

Answer 1

First of all, two-way data binding is here in order to avoid such scenarios.

 <input ng-model='ctrl.field' />

 <button ng-click='ctrl.field = "new value"'>change</button>

Second, there is ng-change directive that works together with ng-model, which can be used to do something when value in the model changed.

 <input ng-model='ctrl.field' ng-change='alert("changed!")' />

If you still want to change value outside of angular directly with DOM, just fire event that angular listen to - blur or keypressed

 <button ng-click='$("#id").val(a); $("#id").trigger("blur")'>change</button>

or

 <button ng-click='angular.element("#id").val(a); angular.element("#id").trigger("blur")'>change</button>