Prefer let over const (not the other way around)

axtk — Sat, 03 May 2025 15:33:39 +0000

Preferring const over let has become sort of mainstream (often enforced with a linting rule), but that actually breaks their semantics and discards the developer's intention.

Semantically, const is a developer's way to communicate to other devs that the variable shouldn't be changed, not that it isn't changed in the current version of code. The developer's intention that a variable shouldn't be changed can't be inferred solely from static analysis of the code, unlike the variable's property of currently being unchanged.

Automatically replacing let with const results in the loss of the distinction between constants specifically marked as never-to-be-changed by a developer with variables that happen to be unchanged, but not inherently unchangeable.

For currently unchanged variables, the prefer const rule also introduces an unnecessary diff when the variable has to be reassigned in a later code change, by converting const to let. And since any const can now be easily switched to let, devs are deprived of a simple way to convey the meaning that a variable is not supposed to be modified.

To fix this, let should be preferred over const by default, with const reserved to things that devs decide shouldn't be changed.

DEV Community: axtk

Prefer let over const (not the other way around)