block-scoped variable
nounUK /blɒk skəʊpt ˈveəriəbl/
US /blɑːk skoʊpt ˈveriəbl/
A variable that only works inside the little section of code where it was made.
The loop counter is a block-scoped variable, so it disappears once the loop finishes.
OTHER MEANINGS
2. A variable declared with let or const that cannot be seen outside its enclosing braces.
Because it is a block-scoped variable, calling it after the if-block throws a ReferenceError.
3. A name whose visibility is limited to the nearest pair of curly braces in a program.
Inside the function, the block-scoped variable shadows the outer one with the same name.
4. A binding that is created fresh each time its block runs, rather than once for the whole function.
Each iteration of the for loop gets its own block-scoped variable, which is why the callbacks log different numbers.