Let vs Const in JavaScript

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Let or const? Which one should you use?

In JavaScript, we commonly declare variables using two keywords: let and const.

When should we use one vs the other?

I always default to using const.


Because const guarantees the value can’t be reassigned.

When programming, I always think that the best thing that I can use is the thing that can harm me the least.

We have an incredible amount of things that can generate problems.

The more power you give to something, the more responsibility you assign to it.

And we don’t generally want that.

Well, it’s debatable, of course, as everything. I don’t want that, and that’s enough for me.

If I declare a variable using let, I let it be reassignable:

let number = 0
number = 1

and in some cases this is necessary.

If I want the variable to be reassignable, let is perfect.

If I don’t, which is in 80% of the cases, I don’t even what that option be available. I want the compiler (interpreter, in the case of JS) to give me an error.

That’s why I default to const every time I declare a variable, and only switch to let when I want the reassign ability to be allowed.