JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/immutable/3.6.2/immutable.js"></script>

JavaScript

var list = Immutable.List([1,2,3,4])
console.log(list.toJS())
var inserted = list.splice(2,0,100)
console.log(list.toJS())
console.log(inserted.toJS())