how to show alert when user scroll to top of div in angular js?

Question

how to show alert when user scroll to top of div in angular js?

7.7k views Asked by user944513 At 26 December 2024 at 12:40

hello could you please how to show alert when scroll to top of div in angular js and same in when user scroll to bottom .Actually I know How to achieve this in jquery using if(this.scrollTop===0).But I am using ionic framework with angular js .So could could you please tell me how to get event when user scroll to top and show the alert .

here is my plunker http://plnkr.co/edit/8bqDi69oiBKTpDvCaOf6?p=preview

<body ng-controller="MyController">
<div style="width:90%;height:150px;border:1px solid red;overflow:auto;overflow-y: scroll">
<div ng-repeat="n in name">{{n.name}}</div>
</div>

Original Q&A

There are 3 answers

Ismapro On 09 June 2015 at 09:17

You have to use a directive so that you connect your element to the backend.

I created a directive which is pretty similar to sebastionbarbier one without the bind part but I guess using link is doing pretty much the same as bind.

    link: function(scope, element, attr) {
element.on('scroll', function() {
  if(element[0].scrollTop == 0)
   alert('show alert');
});

http://plnkr.co/edit/ra6HLvEsPBPHeNqVVI4c?p=preview

SamJB On 09 June 2015 at 10:31

I'm not disagreeing with the other answers, but you should try not to use any global function in Angular, e.g. alert(); you should try to inject dependencies.

Instead, use $window.alert, by injecting $window into your directive. You can then unit test the behaviour by, for example, using Jasmine's spyOn($window, "alert"). E.g.:

spyOn($window, "alert");
expect($window.alert).toHaveBeenCalled();

**sebastienbarbier** · Accepted Answer · 2015-06-09 07:30:49

Angular will not provide you anything for this, you just need to bind a scroll event on your element. In my current project I have just created an event in my controller :

var container = angular.element(document);
container.on('scroll', function() {
    if (container.scrollTop() > 1000) {
        $('#scroll-top-button').addClass('show');
    } else {
        $('#scroll-top-button').removeClass('show');
    }
});
// in your case angular.element(document) should be your div instead of document

It does perform very well (I would expect a if on scroll event to cost some ressource but not really).

Angular directive

Easy way is to define a directive to bind a scroll event and look at position. Based on your code :

angular.module('ionicApp', ['ionic'])
  .directive("scrollable", function() {
    return function(scope, element, attrs) {
      var container = angular.element(element);
      container.bind("scroll", function(evt) {
          if (container[0].scrollTop <= 0) {
              alert('On the top of the world I\'m singing I\'m dancing.');
          }
          if (container[0].offsetHeight + container[0].scrollTop >= container[0].scrollHeight) {
              alert('On the bottom of the world I\'m waiting.');
          }
      });
    };
  })
  .controller('MyController', function($scope, $element) {
    $scope.name = [{ ... }];
  });

Then in your HTML just add the directive

<div scrollable style="width:90%;height:1...

I updated a version on your plunker (v5) which work for me and seems pretty strong for global compatibility. Did it low level ;)

Alternative library

If you want to implement some deeper feature you can use a library like waypoint

Waypoints is a library that makes it easy to execute a function whenever you scroll to an element. http://imakewebthings.com/waypoints/

It works really well too, is very light, and since v3.0 is jQuery free :D. I know some hardcore front-end designer using it without any performance issue.

TechQA.

how to show alert when user scroll to top of div in angular js?

There are 3 answers

Angular directive

Alternative library

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