73.5 13.9 17.45 20.44 27.29 10.6l37.1-37.1c59.28-59.26 59.28-155.7 0-214.96z"/>
      </svg></a> </h2>
<section aria-labelledby="toc_">
<p>Sometimes a computed property needs to update when items are added to, removed from, or replaced in an array.
In those cases we can use the <code>[]</code> array key to tell the property to update at the right time.
We'll use the familiar todo list for our examples:</p>
<div class="filename javascript"><div class="ribbon"></div><span>app/components/todo-list.js</span><pr