Can case/default in JavaScript switch Statement Have Curly Braces?

Starting with ES6, you may use curly braces ({}) with the case/default clauses in a switch statement. This allows you to create a block-scope for case and default, so that you can define local let or const (relative to that block). For example:

// ES6+
const type = 2;

switch (type) {
    case 1: {
        let foo = 'bar';
        console.log(foo);
        break;
    }

    case 2: {
        let foo = 123;
        console.log(foo);
        break;
    }

    // ...
}

// output: 123

As you can see from the example above, using curly braces ({}) creates a block-scope for case (and default). This allows you to use the same variable names in each block (which would have otherwise thrown a SyntaxError).