> So for that reason alone, dynamically typed languages make it harder to maintain a large codebase, because the work that is done by the compiler "for free" is

> So for that reason alone, dynamically typed languages make it harder to maintain a large codebase, because the work that is done by the compiler "for free" is now work that you must do in the form of writing test suites. Static types are not enough to ensure that your algorithm receives correct input, to ensure you that you will need to write tests anyway. So with static languages you get one check "for free" out of the many that you will have to write yourself. If you rigorously write tests for a JavaScript code as you would have for a Java code, it becomes just as reliable.