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Ben_hawk
Ben_hawk

Reputation: 2486

AngularJS : directive watch attribute expression

I want a directive to watch the result of an attribute expression such as:

<div scroll-if="test === selectedTest"></div>

So that it can then react to the change and scroll to the particular element. I seem to be struggling to find out how I can watch for changes to that expression.

Upvotes: 6

Views: 9066

Answers (1)

Carlos Forero
Carlos Forero

Reputation: 411

Use $watch:

app.directive('scrollIf', function() {
  return {
    restrict: 'A',
    link: function(scope, element, attributes) {

      var actionScroll = function(newVal, oldVal) {
        if(newVal!==oldVal) {
          console.log("scrolling");
        }
      }

      scope.$watch(attributes.scrollIf, actionScroll);
    }
  }
});

$watch can evaluate the attribute expression scroll-if, the actionScroll listener will run if this expression is true.

Is necessary to add the condition newVal!==oldVal, because actionScroll always runs the first time. This is explained in the $watch documentation

Upvotes: 12

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