Why are these additional curly brackets added within an else statement?

Upon reviewing some typescript code, I noticed the presence of extra curly braces within an else block. Are these additional braces serving a specific purpose or are they simply used to provide further grouping for two nearly identical code snippets? Considering this originates from a highly popular Microsoft repository, it seems unlikely to be accidental.

  if (playwrightTestPackagePath) {
    require(playwrightTestPackagePath).addTestCommand(program);
    require(playwrightTestPackagePath).addShowReportCommand(program);
    require(playwrightTestPackagePath).addListFilesCommand(program);
  } else {
    {
      const command = program.command('test').allowUnknownOption(true);
      command.description('Run tests with Playwright Test. Available in @playwright/test package.');
      command.action(async () => {
        console.error('Please install @playwright/test package to use Playwright Test.');
        console.error('  npm install -D @playwright/test');
        process.exit(1);
      });
    }

    {
      const command = program.command('show-report').allowUnknownOption(true);
      command.description('Show Playwright Test HTML report. Available in @playwright/test package.');
      command.action(async () => {
        console.error('Please install @playwright/test package to use Playwright Test.');
        console.error('  npm install -D @playwright/test');
        process.exit(1);
      });
    }
  }
}

Source

Answer №1

By using blocks to create new scopes for variables, you can prevent redeclaration errors. For example, if you try to declare const command = ... multiple times within the same scope, you will encounter a

SyntaxError: redeclaration of const command
.

// No errors
{
  const x = 1;
  console.log(x) // 1
}
{
  const x = 2;
  console.log(x) // 2
}
{
  const x = 3;
  console.log(x) // 3
}

// Error
const x = 1
const x = 2 // Uncaught SyntaxError: redeclaration of const x
const x = 3

Using blocks in this way also helps avoid having to name variables with suffixes like command2, command3.

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