The ECMAScript specification allows for creating block-level lexical declarations (let, const, function, and
class) in any block statement or expression. However, when these declarations are made inside the case or
default clause of a switch statement, they are not confined to the block of that case or default
clause. Instead, they apply to the whole switch block but only get initialized when the cases are reached, which can lead to unexpected
behavior.
switch (foo) {
case 1:
let x = 1; // Noncompliant
break;
case 2:
const y = 2; // Noncompliant
break;
case 3:
function f() {} // Noncompliant
break;
case 4:
class C {} // Noncompliant
break;
}
To fix this, you can create a nested block within each case or default clause, ensuring each declaration is properly
scoped to its respective block.
switch (foo) {
case 1: {
let x = 1;
break;
}
case 2: {
const y = 2;
break;
}
case 3: {
function f() {}
break;
}
case 4: {
class C {}
break;
}
}
