SQl-queries run twice in Heroku NodeJS - node.js

Question

Currently I have deployed my website on Heroku with NodeJS.
I came across a weird problem: some SQL-queries are executed twice on mobile, while I don't have this problem on any desktop. So to test if this really was the case, I did a console.log after every database query. In the heroku log I saw that SQL-queries via my mobile were executed twice.
As you can see below, the request is about if you already follow someone. This request has a lot of nested SQL-queries. I don't really know how to properly structure it and therefore it is possible that the problem lies within that. A string is returned which says something about the new relation between you and the user you're trying to follow/unfollow.
So what I'm trying to do:
Check if you follow the person. If this is the case, unfollow the user. Return.
Then, check if the user has a public or private account. If he/she has a public account, you can directly follow the person. Return.
After that, check if you already try to follow the user with a lock. If this is the case, remove the request. Return.
If (3) is not the case, make a request. Return.
When I make this request on my computer, I looked at the heroku logs which showed the following:
2018-03-31T18:13:18.182665+00:00 app[web.1]: execution 1
2018-03-31T18:13:18.203767+00:00 app[web.1]: execution 3
2018-03-31T18:13:18.204511+00:00 app[web.1]: POST /user/follow 200 55.619 ms - 8
2018-03-31T18:13:18.227543+00:00 app[web.1]: execution 4
However, when I did the exact same thing on my mobile, this was showed:
2018-03-31T18:16:24.776125+00:00 app[web.1]: execution 1
2018-03-31T18:16:24.786991+00:00 app[web.1]: execution 1
2018-03-31T18:16:24.793902+00:00 app[web.1]: execution 3
2018-03-31T18:16:24.794795+00:00 app[web.1]: POST /user/follow 200 54.334 ms - 8
2018-03-31T18:16:24.802526+00:00 app[web.1]: execution 3
2018-03-31T18:16:24.803279+00:00 app[web.1]: POST /user/follow 200 46.972 ms - 8
2018-03-31T18:16:24.816062+00:00 app[web.1]: execution 4
2018-03-31T18:16:24.821743+00:00 app[web.1]: execution 4
To make it clear which SQL-statement executed, I made a console.log for each of them with a different name. ('execution1', 'execution2', etc.).
// Check the relationship between the user and the search-user
router.post('/follow', function(req, res, next) {
// Check if the user is logged in
if (!req.session.user) {
return;
}
// Create connection with database
pool.getConnection(function (err, database) {
if (err) throw err;
// Check if you already follow the user
var sql = "SELECT * FROM Followers WHERE user = " + mysql.escape(req.session.user) + " AND following = " + mysql.escape(req.session.userSearch);
database.query(sql, function(err, result, fields) {
console.log("execution 1");
if (err) throw err;
// You follow the user if the if-statement is true
if (result.length != 0) {
// Unfollow the person
var sql = "DELETE FROM Followers WHERE user = " + mysql.escape(req.session.user) + " AND following = " + mysql.escape(req.session.userSearch);
database.query(sql, function(err, result, fields) {
console.log("execution 2");
if (err) throw err;
database.release();
});
return res.send("FOLLOW");
};
// Check if the person has a lock on its account
var sql = "SELECT private FROM Users WHERE user = " + mysql.escape(req.session.userSearch);
database.query(sql, function(err, result, fields) {
console.log("execution 3");
if (err) throw err;
// If the account is public, then the if-statement below is true
if (result[0].private == "0") {
// Follow if the account is not private
var sql = "INSERT INTO Followers (user, following) VALUES (" + mysql.escape(req.session.user) + ", " + mysql.escape(req.session.userSearch) + ")";
database.query(sql, function(err, result, fields) {
console.log("execution 4");
if (err) throw err;
database.release();
});
return res.send("UNFOLLOW");
}
// Prepare data
var sql = "SELECT * FROM PendingFollowers WHERE user = " + mysql.escape(req.session.user) + " AND following = " + mysql.escape(req.session.userSearch);
database.query(sql, function(err, result, fields) {
console.log("execution 5");
if (err) throw err;
// Check if you already try to follow the person
if (result.length == "1") {
// Remove the request
var sql = "DELETE FROM PendingFollowers WHERE user = " + mysql.escape(req.session.user) + " AND following = " + mysql.escape(req.session.userSearch);
database.query(sql, function(err, result, fields) {
console.log("execution 6");
if (err) throw err;
database.release();
});
return res.send("FOLLOW");
}
// Follow and put it in pending
var sql = "INSERT INTO PendingFollowers (user, following) VALUES (" + mysql.escape(req.session.user) + ", " + mysql.escape(req.session.userSearch) + ")";
database.query(sql, function(err, result, fields) {
console.log("execution 7");
if (err) throw err;
database.release();
return res.send("REQUESTED");
});
});
});
})
});
});
EDIT:
HTML:
<button class="buttonFollow" ng-click="follow()"> {{ status }} </button>
AngularJS:
// Status follower
$http.get('/user/status').
then(function(res) {
$scope.status = res.data;
});
// Follow someone
$scope.follow = function() {
$http.post('/user/follow').
then(function(res) {
$scope.status = res.data;
$http.get('/user/informationFollower').
then(function(res){
$scope.following = res.data[0].following;
$scope.followers = res.data[0].followers;
});
});
};
The HTML/AngularJS above is from the page of the user you want to follow. So when the follow-request is done, the number of followers/following of the targeted user will be updated. When I try to follow someone via my computer, the number is incremented with 1 (which is OK). But via my phone, it is incremented with 2. It created a duplicate follow-row in my database on table Followers, but the id is not the same.