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When you try to redeclare variables using let or const in multiple case clauses of a switch statement, you will get a SyntaxError. This happens because, in JavaScript, all case clauses within a switch statement share the same block scope. For example:
1let counter = 1;
2
3switch (x) {
4
5case 0:
6 let name;
7 break;
8
9case 1:
10 let name; // SyntaxError: Identifier 'name' has already been declared
11 break;
12}To avoid this error, you can create a new block scope within each case clause by wrapping the code in curly braces {}. This way, each let or const declaration is scoped only to that block, and redeclaration errors are avoided:
1let counter = 1;
2
3switch (x) {
4
5case 0: {
6 let name;
7 // code for case 0
8 break;
9}
10
11case 1: {
12 let name; // No SyntaxError
13 // code for case 1
14 break;
15}
16}That means, to safely redeclare variables in different cases of a switch statement, wrap each case’s code in its own block using curly braces. This ensures each variable declaration is scoped to its specific case block.
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JavaScript Coding Exercise 22
Test your knowledge with this interactive coding challenge.
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