How does `["length"]` work?
<p>Today when I read undersocre, I found an interesting syntax <strong>["length"]</strong></p>

<p>For example:</p>

<p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-js lang-js prettyprint-override"><code>"hello"["length"] //5
[1,2,3,4]["length"]  //4</code></pre>
</div>
</div>
</p>

<p>This works in Chrome, Firefox and even IE5!</p>

<p>Is this a native js method or does it run in a array way like [1,2,3]["1"] or something like that?</p>