undefined | Better HN

0 pointsubertaco6y ago0 comments

I'm down if you require a let/var/const in front of it:

    if (foo = bar()) { // syntax error!
    }

    if (let foo = bar()) { // works fine
    }

    if (const foo = bar()) { // also works fine
    }

    if (var foo = bar()) { // also also works fine
    }

0 comments

fenomas6y ago

> if (foo = bar()) { // syntax error!

That's already an error in strict mode (which would presumably be on for anyone writing bleeding-edge JS).

AgentME6y ago

It's only an error in strict mode if there's no variable in scope named foo.

dotancohen6y ago

And what if foo had already been defined in the scope?

munificent6y ago

The new one shadows it.

dotancohen6y ago

Local scope might not be what the programmer wants, though, depending on circumstance. Pseudocode:

  i = 3;
  foo = \0;

  while ( i-- ) {
      if ( foo = resultFromFooApi() ) {
          break;
      }
      sleep 1;
  }

  return foo;

j / k navigate · click thread line to collapse

0 pointsubertaco6y ago0 comments

I'm down if you require a let/var/const in front of it:

    if (foo = bar()) { // syntax error!
    }

    if (let foo = bar()) { // works fine
    }

    if (const foo = bar()) { // also works fine
    }

    if (var foo = bar()) { // also also works fine
    }

0 comments

fenomas6y ago

> if (foo = bar()) { // syntax error!

That's already an error in strict mode (which would presumably be on for anyone writing bleeding-edge JS).

AgentME6y ago

It's only an error in strict mode if there's no variable in scope named foo.

dotancohen6y ago

And what if foo had already been defined in the scope?

munificent6y ago

The new one shadows it.

dotancohen6y ago

Local scope might not be what the programmer wants, though, depending on circumstance. Pseudocode:

  i = 3;
  foo = \0;

  while ( i-- ) {
      if ( foo = resultFromFooApi() ) {
          break;
      }
      sleep 1;
  }

  return foo;

j / k navigate · click thread line to collapse