Since sibling comments have pointed out the various ES5 methods and ES6 for-of loops, I'll note two things: 1. This isn't an effort to make all variables `cons

Since sibling comments have pointed out the various ES5 methods and ES6 for-of loops, I'll note two things: 1. This isn't an effort to make all variables `const`. It's an effort to make all objects immutable. You can still reassign any variable, just not mutate objects on the heap (by default) 2. Recursion still works ;)