How to get synchronous SerialPort Read in NodeJS - node.js

Question

Actually working on an automaton project (based on Arduino <-> Serial <-> Raspberry), I seem to be kind of stuck on the serial interface.
Basically, I'm using Express to read/write on some parameter on the arduino by URL in that kind of syntax (http://localhost:3000/parameter/6 or http://localhost:3000/parameter/6/set?value=10).
Since I'm willing to get a simple/short result (as an API), I decided to render a simple json object on each request, there is also no way for me to use post-rendering scripts/frameworks like Socket.io/jQuery/... for this purpose (I'd probably often call those URLs from curl/wget/[other html parsers]).
Now the thing is that there is no problem to write on the port, but for the reading, I'd like to wait for the buffer to be returned from serialport.on('data', function(buffer) { ... }) before rendering the page.
As serialport.on('data', ... ) does seem to be called only once per request, the only way I found for the moment is to redirect to the same page until the buffer has been read, which seem kind of a nasty way of getting things done, also it is incomplete ...
Here's a bit of code to get an idea of the actual logic :
Library :
// -> lib/serial.js - LIBRARY
var SerialPort = require("serialport");
var data = {'state': 0};
var serialPort = new SerialPort(port, {
baudrate: 115200,
parser: SerialPort.parsers.readline('\r\n'),
});
serialPort.on('open', function() {
console.log('Serial port Open');
serialPort.on('data', function(buffer) { data.buffer = buffer, data.state = 1 });
});
function readConfig(cmd, paramNb) {
var cmd = String.fromCharCode(cmd);
var param = String.fromCharCode(paramNb);
if (serialPort.isOpen() == true) {
serialPort.write(cmd + param + '\n', function(err) {
if (err) {
return console.log('Error on write: ', err.message);
}
console.log('message written');
});
}
return data;
};
function writeConfig(cmd, paramNb, value) {
var cmd = String.fromCharCode(cmd);
var param = String.fromCharCode(paramNb);
var value = String.fromCharCode(value);
if (serialPort.isOpen() == true) {
serialPort.write(cmd + param + value + '\n', function(err) {
if (err) {
return console.log('Error on write: ', err.message);
}
console.log('message written');
});
}
};
exports.readConfig = readConfig;
exports.writeConfig = writeConfig;
Route :
// -> parameter.js - ROUTE
var express = require('express');
var router = express.Router();
var serial = require('../../lib/serial');
var sleep = require('sleep');
/* SET Parameter. */
router.get('/:id/set', function(req, res) {
var id = req.params.id;
var value = req.query.value;
serial.writeConfig('b', id, value);
res.json({'result': value, 'id': id});
});
/* GET Parameter. */
router.get('/:id', function(req, res) {
var id = req.params.id;
var buffer = serial.readConfig('a', id);
if (buffer.state != 0) {
res.json({'result': buffer});
}
else {
sleep.usleep(100000);
res.redirect('/api/parameter/' + id); // <- Nasty Bulls**t
}
});
module.exports = router;
The first idea I came up with was to find a synchronous way to read the port so I can call something like this (pseudo-code) :
while (buffer == '') { var buffer = serial.read; }
res.json({buffer});
Anyway thanks everyone.