&gt; The compilation cost for a dynamic language like Javascript is zero, the cost being completely amortized with everything happening directly at runtime.<p>This is one of the big points I always try to make to people. JS compilation is cheap and maybe it&#x27;s faster to spit out some functional code. But all you&#x27;ve really done is pushed the rest of your work to tomorrow. Your type verification happens at runtime, and now instead of your bugs being compiler errors, your bugs are production errors that you&#x27;ve exposed your customers to.<p>With Scala I rarely need to use the debugger. With JS and PHP I have to constantly use the debugger to track down &quot;what type does this variable actually have in this random edge case at runtime?&quot;