I wouldn&#x27;t be surprised if <i>const</i> and arrow functions actually make things slower.  <i>const</i>, or at least a naive implementation of it, requires checking if the value is changed which <i>var</i> does not.  Perhaps that could be equally performant in time.<p>Arrow functions seem like they would take (marginally) longer to parse than explicit <i>function</i> declarations due to having a more verbose AST that does not start with unambiguous tokens.  That, and you have the implicit <i>this</i> binding which must come with a cost.  Again, in time this might be okay.