ES2015 const is not about immutability

<span style="color: #333333;">const</span> creates an immutable binding

To make an object’s values immutable, use Object.freeze(). It has been around since ES5 and is widely available nowadays.

<span class="keyword">const</span> foo = <span class="built_in">Object</span>.freeze({
	<span class="string">'bar'</span>: <span class="number">27</span>
});
foo.bar = <span class="number">42</span>; <span class="comment">// throws a TypeError exception in strict mode;</span>
              <span class="comment">// silently fails in sloppy mode</span>