Mutable variable is accessible from closure with promise and loop

Question

I use the following code to generate a unique token for a user. Data for users is stored on MongoDB so I use promise to handle asynchronous talking to the db. In WebStorm I receive this warning : Mutable variable is accessible from closure with promise and loop. and I know there have been posts on SO about this thing, but I my case is more complicated. I know I may not even need to worry about it as I only use the last value of token but what I want to solve this issue in a correct way ?

  var generateToken = function(userId) {
        User.findOne({userId: userId}, function(err, user) {
            if (user !== null) {
                var loop = true;
                while (loop) {
                    var token = Common.randomGenerator(20);
                    User.find({tokens: token}, function(err, result) {
                        if (err) {
                            loop = false;
                            return Promise.reject('Error querying the database');
                        } else {
                            if (result.length === 0) {
                                if (user.tokens === undefined){
                                    user.tokens.push(token);
                                }
                                loop = false;
                                return Promise.resolve(token);
                            }
                        }
                    });
                }
            } else {
                return Promise.reject('UserNotFound');
            }
        });
   };

I came up with the following solution , is it correct ?

var generateToken = function(userId) {
    User.findOne({userId: userId}, function(err, user) {
        if (user !== null) {
            var loop = true;
            while (loop) {
                var token = Common.randomGenerator(20);
                (function(e){
                    User.find({tokens: e}, function(err, result) {
                        if (err) {
                            return Promise.reject('Error querying the database');
                        } else {
                            if (result.length === 0) {
                                if (user.tokens === undefined){
                                    user.tokens = [];
                                }
                                user.tokens.push(e)
                                return Promise.resolve(e);
                            }
                        }
                    });
                })(token);
            }
        } else {
            return Promise.reject('UserNotFound');
        }
    });
};

NOTE As @Alex Nikulin suggested , I flipped loop to false before sending back the result of the promise. But still it's an infinite loop as it doesn't go into the User.find({tokens: e})....

Answer 1

Your problem is that, return statement is within function, not within loop.Your loop is infinite. I has decomposited your code.Or simply make loop false, when you resolve/reject promise. Also my code will wait each answer from User, and error will gone. And your variant with wrap function is correct (function(e){})(token) .

var generateToken = function(userId) {
        return new Promise(function(resolve, reject) {
                User.findOne({userId: userId}, function(err, user) {
                    if (user !== null) {
                            userTokenIterator(user,resolve, reject);   
                        } else {
                            reject('UserNotFound');
                        }
                });
        });
       };

    var addTokenToUser = function(token,user){
            return new Promise(function(resolve, reject) {
                      User.find({tokens: token}, function(err, result) {
                        if (err) {
                                reject('Error querying the database');
                        } else {
                                   var result = result.length === 0;
                                if (result) {
                                      if(!user.tokens)  {
                                             user.tokens = []
                                      }
                                      user.tokens.push(token);
                                 } 
                                    resolve(result);    
                        }
            });
            }); 
    };
    var userTokenIterator = function (user, resolve, reject){
            var token = Common.randomGenerator(20);
        addTokenToUser(token, user).then(function(result){
                  if(result) {
                      resolve(token);
                  }else{ 
                      userTokenIterator(user,resolve, reject)
                  }                     
            },function(error){
                   reject(error);
            }); 
    };