docs: no-constant-condition: Add multi-comparison example

[SebastianSimon]

Prerequisites checklist

• I have read the contributing guidelines.

What is the purpose of this pull request? (put an "X" next to an item)

[X] Documentation update
[ ] Bug fix (template)
[ ] New rule (template)
[ ] Changes an existing rule (template)
[ ] Add autofix to a rule
[ ] Add a CLI option
[ ] Add something to the core
[ ] Other, please explain:

What changes did you make? (Give an overview)

I have added the common beginners’ mistake of incorrectly comparing a value against multiple other values. ESLint triggers the no-constant-condition error for code such as this, but the documentation doesn’t clearly point out what is wrong and how to fix it.

if(input === "hello" || "bye"){ // Unexpected constant condition. (no-constant-condition)
  output(input);
}

Given the large number of duplicates on Stack Overflow, I feel like this is an important example missing from the documentation.

Is there anything you'd like reviewers to focus on?

• Is this an appropriate addition to the documentation?
• Should this example be merged into the existing code blocks or be separate as in the PR?
• Should a subheading be added for this example for easy linking?

Feel free to edit as needed!

[netlify]

✅ Deploy Preview for docs-eslint ready!

Name	Link
🔨 Latest commit	dcefbea
🔍 Latest deploy log	https://app.netlify.com/sites/docs-eslint/deploys/63cf2f63ccfbfa0009590a89
😎 Deploy Preview	https://deploy-preview-16776--docs-eslint.netlify.app/rules/no-constant-condition
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site settings.

[eslint-github-bot]

Hi @SebastianSimon!, thanks for the Pull Request

The first commit message isn't properly formatted. We ask that you update the message to match this format, as we use it to generate changelogs and automate releases.

• The commit message tag wasn't recognized. Did you mean "docs", "fix", or "feat"?
• There should be a space following the initial tag and colon, for example 'feat: Message'.
• The first letter of the tag should be in lowercase

To Fix: You can fix this problem by running git commit --amend, editing your commit message, and then running git push -f to update this pull request.

Read more about contributing to ESLint here

[mdjermanovic]

• Should this example be merged into the existing code blocks or be separate as in the PR?

I think it would be better to merge this example into the existing code blocks.

[nzakas]

@SebastianSimon are you still working on this?

[SebastianSimon]

@SebastianSimon are you still working on this?

I was waiting for more feedback, but I guess after the one comment with the one thumbs up, there’s not going to be anything else, therefore I just made that change, so now you can merge this, unless there’s anything else you expect me to act on. I don’t really have a strong opinion on these feedback points.

Although, looking at the other examples more closely, there are quite a few of those semantic errors, just like the example I’ve added, so unifying the examples really does make more sense. Thanks!

[snitin315]

LGTM. Thanks for contributing.

[mdjermanovic]

LGTM, thanks!