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When rendering thousands of items in AngularJS, the choice of ng‑repeat strategy determines performance. This guide compares default, track‑by $index, and track‑by unique id approaches, explains trade‑offs, and walks through a benchmark that shows why a stable id is the best choice.
Learn how to add a track by expression to AngularJS ng-repeat to reuse DOM nodes and avoid costly rebuilds when large lists change.
Problem: ngRepeat:dupes error when rendering duplicate items AngularJS 1.x throws the ngRepeat:dupes error when an ng-repeat directive encounters two or more items that produce the same tracking value. By default, the tracking value is the item itself, so primitive duplicates or identical objects trigger the error. To avoid the error, a track by expression m