emberjs.com/classes/Ember.Templates.helpers.html#toc_specifying-keys">using the <code>key</code> option with an each
helper</a>
can improve re-render performance when an array is replaced with another
containing similar items.</p>
<h3 id="toc_accessing-an-items-index">Accessing an item's <code>index</code> <a href="#toc_accessing-an-items-index"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512">
        <path d="M326.61 185.4c59.75 59.8 58.93 155.69.36 214.58-.1.12-.24.25-.36.37l-67.2 67.2c-59.2