How to increment external variable value within MySQL Query in NodeJS

Question

I'm developing an API using NodeJS and MySQL.

The create API takes a Request as an object and executes the queries one by one inside the for statement.

And I created a variable called createCnt externally to count the success of the query, and I want to use this value when sending a response.

But since the current code is callback, the order of execution is not guaranteed.

Therefore, if you print createCnt outside of a query, -1 always appears.

How can I increment a variable outside the query inside the query?

create API

exports.create = async (req, res, next) => {
  const { userId } = req.decoded;
  const { createList } = req.body;

  let createCnt = undefined;

  try {
    createCnt = -1;

    for (let i = 0; i < createList.length; i++) {
      const { content, color, date, colorLevel } = createList[i];

      let sql = `INSERT INTO post (content, color, date, colorLevel, userId) VALUES (?, ?, ?, ?, ?)`;

      Post.query(
        sql,
        [content, color, date, colorLevel, userId],
        async (err, result) => {
          if (err) {
            return next(err);
          }
          return await (createCnt += 1); // increase OK
        }
      );
    }
  } catch (error) {
    console.log(error);
  } finally {
    console.log(createCnt); // always "-1"
  }
};

Answer 1

The problem is that Post.query is async. You should use it with await in order to to get it working as you expected.