Requesting underscore demarcation for no-unused-vars

The rule no-unused-vars is very useful. However there are times at which its current structure is at odds with other peoples’ APIs.

Consider the case of a page error handler to express.js, whose signature is roughly

app.use(function(err, req, res, next) { ... });

If you want to write a 404 handler that looks at what the actual error was, and sets things on the response, but doesn’t care what the request is (say, maybe you’re making an imgur clone,) then you’re out of luck: there is no way to write that which won’t ring eslint’s bell.

Could eslint be extended to do what erlang does? Prefixing a name with an underscore in erlang suppresses non-use detection. Then we could just name them _req and _next and the problem goes away.

[zckrs]

Since 2014 the rule no-unused-vars have news options.

You can use http://eslint.org/docs/rules/no-unused-vars#argsignorepattern

Example in package.json

"eslintConfig": {
    "rules": {
      "no-unused-vars": ["error", { "argsIgnorePattern": "next" }]
    }
  }

[StoneCypher]

cheers, thanks 😄