Data-binding in Angular ceases to function properly in the presence of duplicate values within an

My HTML code is set up to bind the $scope.comments array to an unordered list;

<div ng-app="" ng-controller="commentController">
    <ul>
        <li ng-repeat="c in comments">
            {{ c }}
        </li>
    </ul>
<div>

After that, I have a script that initializes and allows for the addition of more items to the list;

<script>
    function commentController($scope){
        $scope.comments = ['Hi There.'];
        $scope.addComment = function(){
            $scope.comments.push($scope.newcomment);
            $scope.newcomment='';
        };
    };   
</script>

Everything works perfectly until I try to add a duplicate item. Upon debugging, I noticed that while Javascript does push the duplicate item to the array, Angular data binding fails to update the list.

Can anyone provide any insight into why this might be happening or point out any mistakes in my approach?

Answer №1

Below is the code snippet you can use:

<div ng-app="" ng-controller="commentController">
    <ul>
        <li ng-repeat="c in comments track by $index">
            {{ c }}
        </li>
    </ul>
<div>

This code uses track by $index to track the array element using index instead of value. For more information, refer to this link.

Answer №2

To ensure proper tracking, it is recommended to track by index rather than values when using ng-repeat. Simply modify the following line within the ng-repeat loop:

ng-repeat="c in comments track by $index"

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