Explode a string into a hashmap for searching?
<p>I have a string like this being returned from my backend:</p>

<pre><code>"1,2,3,4,5,6"
</code></pre>

<p>I have a large array locally and want to display only those items not in this list, so I was thinking of exploding this string into an array but how can I search efficiently? As far as I know there are no hashmaps in JS so how does one do this? I just need to check for key existence.</p>
