node.js mySQL获取记录

Question

Coming from a strong PHP/MySQL and Python/MySQL background, I can't seem to wrap my head around the asynchronous nature of javascript/node.js, so I've started exploring 'promises.' I have a sort-of implementation, but in the output, the best I can get get is [object Promise] as a result...

How do I convert the [object promise] to an array or a value that I can render on the page?

index.html:

<button type="button" onclick="get_row();">
  Get Row
</button>
<div id="output"></div>
<script src="./js/app.js"></script>

app.js:

var db = require('./js/db.js');

function get_row() {
  var result = db.dosql('SELECT * from table LIMIT 1')
  result.then(
     document.getElementById("output").innerHTML = result;
  )
};

db.js:

var mysql       = require('mysql');
var credentials = {
  host     : 'localhost',
  user     : 'user',
  password : 'pass',
  database : 'schema'
};


function dosql(sql) {
  return new Promise((resolve, reject) => {
    var connection = mysql.createConnection(credentials);
    connection.connect();
    connection.query(sql, (err, result) => {
      if (!err){
        return resolve(result)
      }else{
        return reject(err)
      }
    });
    connection.end();
  })
}

exports.dosql = dosql;

Footnote: I'm reasonably certain I have no idea what I'm doing here -- and accept that any of this code could be a complete bastardization of javascript and promises.

UPDATE:

I stumbled into rewriting app.js like so:

function get_row() {
  var result = db.dosql('SELECT * from table LIMIT 1')
  result.then(function(value){
    document.getElementById("output").innerHTML = value[0].row;
  })
};

Which does indeed output the expected value for row. Which works... but I'm not sure why...

Answer 1

Once I was lost, now I'm found (callback has to 'do something' with the value via a function):

app.js:

function get_row() {
  var result = db.dosql('SELECT * from table LIMIT 1')
  result.then(function(value){
    document.getElementById("output").innerHTML = value[0].row;
  })
};