JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/immutable/3.7.5/immutable.js"></script>

JavaScript

var obj = Immutable.Map({categories: {1: 'a', 2: 'b'}});
var output = obj.getIn(['categories', 1]);
alert(output);