callback-return

Calling a callback doesn't stop the function. If you call callback(err) in an if and forget to return, the code below it runs too, and the callback often gets called a second time.

The rule reports a call to callback, cb or next inside a function, unless the call is returned, is followed by a return that ends its block, or is the function's last statement.

ESLint has deprecated this rule. Use n/callback-return instead.

Examples#

function load(path, callback) {
  readFile(path, (err, text) => {
    if (err) {
      callback(err);
    }
    callback(null, JSON.parse(text));
  });
}

function load(path, callback) {
  readFile(path, (err, text) => {
    if (err) {
      return callback(err);
    }
    callback(null, JSON.parse(text));
  });
}

function check(request, response, next) {
  if (!request.user) {
    next(new Error("Not signed in"));
    return;
  }
  next();
}

Options#

The only option is the list of names that count as callbacks. It replaces the default, ["callback", "cb", "next"]. A name can be a path such as "response.send".

function handle(request, response) {
  if (!request.user) {
    response.send(401);
  }
  response.send(200);
}

With the same list, callback isn't checked anymore:

function load(err, callback) {
  if (err) {
    callback(err);
  }
  finish();
}

When not to use it#

The rule only looks at the name, so it can't tell a callback from any other function called next. You don't need it in code that uses promises and async functions.