The JavaScript block statement

In the first scrap of this blog I’d like to make a case for a great little feature that I rarely see used in the wild.

• Want to organize your code a little bit better?
• Have a hard time coming up with another name for the same variable?
• Want to run the same code multiple times in the console or a REPL?

Use blocks! Let’s take a bogus unit test:

function test() {
  const type = 'some';

  const thing = getThing(type, 1);
  assert.equal(thing, 1);

  // Ehm... how to call this `thing` now...?
  const thing2 = getThing(type, 2);
  assert.equal(thing2, 2);
}

Specifically for unit tests you could argue that this particular case should be separated in two unit tests, but sometimes that’s just not what you want. You can use blocks instead:

function test() {
  const type = 'some';

  {
    const thing = getThing(type, 1);
    assert.equal(thing, 1);
  }

  {
    const thing = getThing(type, 2);
    assert.equal(thing, 2);
  }
}

A pair of curly braces are the delimiters of the blocks, and define a new scope for let, const and function declarations.

Neat!