I tend to go by the following rules: Use const by default. If I need let, see if I can refactor to using const. I've found that actually I can go far without

I tend to go by the following rules: Use const by default. If I need let, see if I can refactor to using const. I've found that actually I can go far without using let, improving my code along the way. I see a pattern from colleagues. They initialise a variable using let and then branch to figure out what should go inside it. That can be replaced by a pure function. For loops tend to be the next thing. In that case, they can be replaced by higher order functions/methods without detriment to clarity (usually an improvement). Perhaps the move towards iterators, with async support, will make it more common and legitimate. I haven't yet used those in a codebase but perhaps let in that instance leads to clearer code.