What is the best way to adjust the opacity of a view when a SELECT option is changed?

Question

What is the best way to adjust the opacity of a view when a SELECT option is changed?

While it may be tempting to take a shortcut and ignore MVC principles, I am determined to learn how to work harmoniously with Angular. I have been struggling with seemingly trivial issues, such as this one.

My goal is for div#thisShouldFade to smoothly fade out when a new option is selected, then fade back in with the updated data.

Below is the HTML code:

<body ng-app="MyApp">
  <div ng-controller="MyController as myCtrl">

    <select ng-model="myCtrl.currentThing" ng-options="object.name for object in myCtrl.things">
      <option value="">--choose a thing--</option>
    </select>

    <div id="thisShouldFade">{{myCtrl.currentThing.data}}</div>

  </div>
</body>

And here's the JavaScript code:

angular.module("MyApp", [])

  .controller("MyController", function(){
    this.things = [
      { name: "Thing One",   data: "This is the data for thing one" },  
      { name: "Thing Two",   data: "This is the data for thing two" },  
      { name: "Thing Three", data: "This is the data for thing three" }
    ];

    this.currentThing = null;
  })

For reference, here's the Plunk link:

http://plnkr.co/edit/RMgEOd6nrT9lFQlslDR0?p=preview

I've experimented with various methods using ngAnimate to apply classes with CSS transitions, but it seems that the model changes too quickly due to being bound to the SELECT.

If anyone has an effective Angular-based approach, I would greatly appreciate your advice. I would prefer not to rely on jQuery for this task. However, you can see a jQuery example demonstrating the desired effect here:

http://plnkr.co/edit/SIFZI95Xy5IzgOQN0qVU?p=preview

javascript angularjs css-animations

Answer 1

Answer №1

Experience a clever workaround to achieve your desired outcome by utilizing transition delays and an ng-repeat. While not without its flaws, this method introduces a brief delay when transitioning from no selection to a selection that matches the transition delay:

angular.module("MyApp", ['ngAnimate'])

.controller("MyController", function() {
  this.things = [{
    name: "Thing One",
    data: "This is the data for thing one"
  }, {
    name: "Thing Two",
    data: "This is the data for thing two"
  }, {
    name: "Thing Three",
    data: "This is the data for thing three"
  }];

  this.currentThing = [];
})

.animate {
  position: absolute;
  transition: all 0.5s;
}
.animate.ng-enter {
  opacity: 0;
}
.animate.ng-enter-active {
  opacity: 1.0;
  transition-delay: 0.4s;
  -webkit-transition-delay: 0.4s;
}
.animate.ng-leave {
  opacity: 1.0;
}
.animate.ng-leave-active {
  opacity: 0;
}

<script src="//cdnjs.cloudflare.com/ajax/libs/angular.js/1.3.16/angular.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/angular.js/1.3.16/angular-animate.min.js"></script>

<body ng-app="MyApp">
  <div ng-controller="MyController as myCtrl">
    <select ng-model="myCtrl.currentThing[0]" ng-options="object.name for object in myCtrl.things">
      <option value="">--choose a thing--</option>
    </select>
    <div ng-repeat="thing in myCtrl.currentThing" class="animate">{{thing.data}}</div>
  </div>
</body>

Answer 2

Experience a clever workaround to achieve your desired outcome by utilizing transition delays and an ng-repeat. While not without its flaws, this method introduces a brief delay when transitioning from no selection to a selection that matches the transition delay:

angular.module("MyApp", ['ngAnimate'])

.controller("MyController", function() {
  this.things = [{
    name: "Thing One",
    data: "This is the data for thing one"
  }, {
    name: "Thing Two",
    data: "This is the data for thing two"
  }, {
    name: "Thing Three",
    data: "This is the data for thing three"
  }];

  this.currentThing = [];
})

.animate {
  position: absolute;
  transition: all 0.5s;
}
.animate.ng-enter {
  opacity: 0;
}
.animate.ng-enter-active {
  opacity: 1.0;
  transition-delay: 0.4s;
  -webkit-transition-delay: 0.4s;
}
.animate.ng-leave {
  opacity: 1.0;
}
.animate.ng-leave-active {
  opacity: 0;
}

<script src="//cdnjs.cloudflare.com/ajax/libs/angular.js/1.3.16/angular.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/angular.js/1.3.16/angular-animate.min.js"></script>

<body ng-app="MyApp">
  <div ng-controller="MyController as myCtrl">
    <select ng-model="myCtrl.currentThing[0]" ng-options="object.name for object in myCtrl.things">
      <option value="">--choose a thing--</option>
    </select>
    <div ng-repeat="thing in myCtrl.currentThing" class="animate">{{thing.data}}</div>
  </div>
</body>

Answer 3

Answer №2

When you need to manipulate the DOM, one common approach is to create a directive.

I've created a straightforward example of a directive to demonstrate how it can be implemented; check it out here: http://jsfiddle.net/9ydqvzms/. This example assumes that a variable named show is present in the controller.

$scope.show = {
    data: null
};

This issue could also be resolved by utilizing an appropriate scope within the directive or implementing some form of callback function.

app.directive('optionFader', function () {
    return {
        link: function(scope, element, attrs) {
            scope.$watch(attrs.optionFader, function(newValue, oldValue) {
                if (oldValue == newValue && newValue === undefined) return;
                
                var qelem = $(element);
                if (!scope.show.data) {
                    // Fade in directly if no previous value is available
                    qelem.fadeOut(0);
                    scope.show.data = newValue;
                    qelem.fadeIn(1000);
                } else {
                    qelem.fadeOut(1000, function() {
                        if (newValue) {
                            scope.show.data = newValue;
                            // Apply changes since we're outside the digest cycle
                            scope.$apply();
                        }
                        qelem.fadeIn(1000);
                    });
                }
            });
        }
    };
});

In essence, this directive monitors changes in a specific value (in this case, currentThing.data) and updates another scope variable (show.data) which dictates the displayed value.

To use this in your HTML, simply add the attribute below:

<div id="thisShouldFade" option-fader="currentThing.data">{{show.data}}</div>

Answer 4

When you need to manipulate the DOM, one common approach is to create a directive.

I've created a straightforward example of a directive to demonstrate how it can be implemented; check it out here: http://jsfiddle.net/9ydqvzms/. This example assumes that a variable named show is present in the controller.

$scope.show = {
    data: null
};

This issue could also be resolved by utilizing an appropriate scope within the directive or implementing some form of callback function.

app.directive('optionFader', function () {
    return {
        link: function(scope, element, attrs) {
            scope.$watch(attrs.optionFader, function(newValue, oldValue) {
                if (oldValue == newValue && newValue === undefined) return;
                
                var qelem = $(element);
                if (!scope.show.data) {
                    // Fade in directly if no previous value is available
                    qelem.fadeOut(0);
                    scope.show.data = newValue;
                    qelem.fadeIn(1000);
                } else {
                    qelem.fadeOut(1000, function() {
                        if (newValue) {
                            scope.show.data = newValue;
                            // Apply changes since we're outside the digest cycle
                            scope.$apply();
                        }
                        qelem.fadeIn(1000);
                    });
                }
            });
        }
    };
});

In essence, this directive monitors changes in a specific value (in this case, currentThing.data) and updates another scope variable (show.data) which dictates the displayed value.

To use this in your HTML, simply add the attribute below:

<div id="thisShouldFade" option-fader="currentThing.data">{{show.data}}</div>

What is the best way to adjust the opacity of a view when a SELECT option is changed?

Answer №1

Answer №2

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