I wrapped with try-catch block but app crashed

Question

I am trying to throw an error in the following syntex:

  if(err) throw err

What I expect is to print the log by the line of "console.log(err)" instead of app crashed.

However, this occurs an error with app crashed and says

throw err; // Rethrow non-MySQL errors
        ^

Error: Error: ER_DUP_ENTRY: Duplicate entry 'test4' for key 'nickname_UNIQUE'

I cannot figure out why this happens and need helps from the experties.

code :

 api.post('/', (req, res) => {
    const email = req.body.email
    const nickname = req.body.nickname
    const password = req.body.password
    const thumbnail = req.file
    const type = req.body.type

    const hasherCallback = (err, pass, salt, hash) => {
      if (err) throw err

      const sql = `INSERT INTO users set ?`
      const fields = { nickname, email, 'password': hash, salt, thumbnail, type }
      const queryCallback = (err) => {
        if (err) throw err

        return res.json(messages.SUCCESS_MSG)
      }

      conn.query(sql, fields, queryCallback)
    }
    try {
        return hasher({ password }, hasherCallback)
    } catch (err) {
      //handle errors here
      console.log(err)
    }
  })

  return api
}

//Error : Error: Error: ER_DUP_ENTRY: Duplicate entry 'test4' for key 'nickname_UNIQUE'

Answer 1

I found that I cannot throw errors in async function so I tried using callback.

api.post('/', (req, res) => {
    const email = req.body.email
    const nickname = req.body.nickname
    const password = req.body.password
    const thumbnail = req.file
    const type = req.body.type

    const errorHandle = (callback) => {
      const hasherCallback = (err, pass, salt, hash) => {
        if (err) return callback(err)

        const sql = `INSERT INTO users SET ?`
        const fields = { nickname, email, 'password': hash, salt, thumbnail, type }
        const queryCallback = (err) => {
          if (err) return callback(err)

          return res.json(messages.SUCCESS_MSG)
        }
        conn.query(sql, fields, queryCallback)
      }

      return hasher({ password }, hasherCallback)
    }

    return errorHandle((err) => {
      //This one equals console.log({ status: 'error' message: err })
      return res.status(500).json(messages.ERROR(err))
    })
  })

This prints log what I want instead of app crashed.

 {
    "status": "error",
    "message": {
        "code": "ER_DUP_ENTRY",
        "errno": 1062,
        "sqlMessage": "Duplicate entry 'test4' for key 'nickname_UNIQUE'",
        "sqlState": "23000",
        "index": 0,
        "sql": "INSERT INTO users SET `nickname` = 'test4', `email` = 'test4@test.com', `password` = 'FXxSpPBNFfL1KGS0sWn19N191Hj0FXtnCWwMspneVIvwB5UgPBI0MjBskEnHby357j/3VKWM7ffi/5yD5CiIRyAGMWnTaStzbVX/hhD1/y91UW9b8etWpV5koKcn9QsmD9BozX1+wkve66lTNoFUHDWA0BDj4j8O7ltsD4698LQ=', `salt` = 'cu7GlOjK4drxV/SD4CBJtiW5yirc5/TpaAroCBbCQtOy4Asr8rGvTrxArXHmPH6ADTtHlXvUEEoeUD73LS654Q==', `thumbnail` = NULL, `type` = 'local'"
    }
}