Meh... I agree where he comes from (when working on large projects, muttability can introduce bugs), but many languages have solved it, similar by having two ty

Meh... I agree where he comes from (when working on large projects, muttability can introduce bugs), but many languages have solved it, similar by having two types, 'let' and 'var', or 'const' in front of a variable. But, there is practicality in the ability of being able to change a var, and not having to create a new object every time you change one of its members. It models real nature/physics better. It looks like He is asking that 'const' be the default, and 'var' should be explicit, which makes sense.