Is using track by in Angular 1.6 with ng-repeat still considered beneficial? Does it contribute to better performance?
Is using track by in Angular 1.6 with ng-repeat still considered beneficial? Does it contribute to better performance?
If each item in your array is uniquely identified by a property, it is recommended to use that property for the track by part of your ng-repeat directive. Here's an example:
$scope.items = [
{id: 1, name: "some name"},
{id: 2, name: "some name"}
];
Your ng-repeat should be like this:
ng-repeat="item in items track by item.id"
The AngularJS documentation suggests:
Best Practice: If you have objects with a unique identifier property, use it for tracking instead of the object instance, e.g. item in items track by item.id. This approach improves rendering performance, especially for large collections, as ngRepeat does not need to recreate DOM elements for already rendered items even if the underlying objects are replaced.
However, if your array may contain duplicate values like this:
$scope.items = [
{name: "name1"},
{name: "name1"},
{name: "name2"},
];
In such cases, your ng-repeat should look like this:
ng-repeat="item in items track by $index"
You can test the performance impact of using or not using track by in this fiddle.
Check out the original article on improving ng-repeat performance with track by.
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