JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/immutable/3.8.2/immutable.js"></script>
<p>
  Open up dev tools and go the to memory tab. Watch the memory usage of this tab. Then
</p>
<button id="makeArray" onclick="makeArray()">
  make array
</button>
<button id="makeImmutable" onclick="makeImmutable()" disabled="disabled">
  make immutable
</button>
<p>
  To try again, close this tab and open it again to flush any cache
</p>

JavaScript

var a = [];
var b = Immutable.List();

function makeArray() {
	for (var i = 0; i < 1000000; i++) {
  	a.push({
    	id: i,
      name: 'name' + i,
    });
  }
  document.getElementById('makeImmutable').disabled = false;
}

function makeImmutable() {
  for (var i = 0; i < 1000000; i++) {
  	b = b.push(Immutable.Map({
    	id: i,
      name: 'name' + i,
    }));
  }
}