standard rejects a common use case for the `while` loop

[75lb]

this is one of the most common use cases for the while loop:

  while (value = getValue(something)) {
    ...
  }

unfortunately, standard rejects it (Expected a conditional expression and instead saw an assignment.) Is there any particular reason?

[LinusU]

Wrap it in double parenthesis to explicitly say that you want assignment. This is a great rule since it catches errors where you've missed an equal sign.

while ((value = getValue(something))) {
  ...
}

[dcousens]

Doesn't make it any less confusing IMHO. I guess the following is an alternative anyway:

while (true) {
  value = getValue(something)
  if (!value) break
}

[feross]

@dcousens I've seen the double-paren frequently used as a way to indicate you meant assignment not an equality test. But I agree that this code is generally best avoided. Sometimes though, it's the cleanest way to solve a problem.

[75lb]

well we have two suggested alternative styles but we need one-to-rule-them-all, so let's go with @LinusU 's approach 👍

[dcousens]

@75lb well, you can't rule the latter out, as it is a valid construct in many different situations.
Compare that to the approach by @LinusU, which is only useful for this (IMHO).

I'm OK with either, just pointing out that if a choice was to be made, you could only meaningfully rule out the approach by @LinusU.

[feross]

Yeah, both approaches are perfectly fine :)

[rstacruz]

i just realized the double-parens rule is not documented... we should fix that

[rstacruz]

it might be helpful to point out that this is common in if conditions too:

if (m = text.match(/...*?/)) {
  // ...
} else if (m = text.match(/...*?/)) {
  // ...
} else {
  // ...
}

[feross]

@rstacruz Yep, agree. Do you want to send a PR?