jargon

Frontend & browser·JavaScript in the browser

you got 'cannot access before initialization' on a `const` that is clearly declared right there in the file.

Temporal dead zone

Also calledTDZ

The window between entering a scope and the point where a `let` or `const` is initialised, during which reading it throws instead of returning undefined. It exists to turn a silent `var` bug into a loud error. It surprises people in circular module imports and in class field ordering, where the access happens earlier than reading the file top to bottom suggests.

Commonly confused with