If I do this with Express it fails:
res.send(13245)
It says:
express deprecated res.send(status): Use res.sendStatus(status) instead src/x.js:38:9
(node:25549) UnhandledPromiseRejectionWarning: RangeError [ERR_HTTP_INVALID_STATUS_CODE]: Invalid status code: 13245
It's because it consider 13245 might be a status code.
I want to return 13245 anyway, is there a way do do this?
You have to return a String (see http://expressjs.com/en/api.html#res.send):
res.send('13245')
If you check documentation http://expressjs.com/en/api.html#res.send, the value just can be a Buffer object, a String, an object, or an Array. What if you send
res.send({ value: 13245 })
and then in the other side you just need to grab the value (e.g. body.value).
You can try res.send('13245'); or you can try res.send(""+13245).
You are getting that error because Express assumes you are trying to send a status code. So you can send it as a string and Express will accept it or join it to a string and Express should think you are sending back just some plain number and yes always check the docs when you run into trouble:
http://expressjs.com/en/api.html#res.send
let say you are doing a calculation and you wanna send the result.
app.post("/transaction", (req, res) => {
const a = req.body.amount;
const b = req.body.price;
const total = a*b;
res.send(total.toString());
});
Related
I encountered this weird problem when experimenting with JavaScript's URL object
here is the demo : https://codesandbox.io/s/fervent-wilbur-15kyt?file=/src/index.js
so the endpoint is https://jsonplaceholsdsdsdder.typicode.com/todos/,
The key id can be integer as its value. So https://jsonplaceholder.typicode.com/todos/?id=4 is valid. and https://jsonplaceholder.typicode.com/todos/?id=dsdsd is not valid.
I found that using Fetch to make the request https://jsonplaceholder.typicode.com/todos/?id=4 will still return a response with a status code 200.
const inputEl = document.querySelector("#input");
const endpoint = new URL("https://jsonplaceholder.typicode.com/todos/");
inputEl.addEventListener("input", async e => {
const { value: text } = e.target;
endpoint.searchParams.set("id", text);
const repsonse = await fetch(endpoint).catch(console.error);
const data = await repsonse.json();
console.log(repsonse.status); // 200
console.log(data); // []
});
However if we construct the URL directly like this
https://jsonplaceholsdsdsdder.typicode.com/todos/dd. this will actually return a response with 404 status code.
search params are not a part of the resource location. They are optional and have to be manually accessed by the server processing the request.
https://jsonplaceholder.typicode.com/todos/ is a valid resource location that has been set up by jsonplaceholder.com.
https://jsonplaceholder.typicode.com/todos/?id=4 is a valid resource location because anything after the question mark (?) is a parameter and parameters are not considered to be apart of the resource location so it is still valid.
https://jsonplaceholsdsdsdder.typicode.com/todos/dd is not a valid resource location because jsonplaceholder.com has not exposed a resource with that path.
This is because of the way the API works server side.
If you try and use that route, you'll get the 404 error because that specific route wasn't found.
If you use the searchParams.set method, it's just a parameter that the backend will use to filter the full list of todos, in which case the call was made successfully, hence the 200 response code. but the response results were empty, hence the empty array [].
So I am receiving JSON over a websocket from a chargepoint using OCPP 1.6 JSON.
I am trying to parse the message and respond appropriately, depending on what the message is, using Node.js
Here is the message that I recieve:
[ 2,
'bc7MRxWrWFnfQzepuhKSsevqXEqheQSqMcu3',
'BootNotification',
{ chargePointVendor: 'AVT-Company',
chargePointModel: 'AVT-Express',
chargePointSerialNumber: 'avt.001.13.1',
chargeBoxSerialNumber: 'avt.001.13.1.01',
firmwareVersion: '0.9.87',
iccid: '',
imsi: '',
meterType: 'AVT NQC-ACDC',
meterSerialNumber: 'avt.001.13.1.01' } ]
In this case it is the 'BootNotification' message, to which I need to respond with an 'Accepted' message.
Here is my code:
const WebSocket = require('ws');
const wss = new WebSocket.Server({ port: 8080 });
wss.on('connection', function connection(ws) {
ws.on('message', function incoming(message) {
//Make incoming JSON into javascript object
var msg = JSON.parse(message)
// Print whole message to console
console.log(msg)
// Print only message type to console. For example BootNotification, Heartbeat etc...
console.log("Message type: " + msg[2])
// Send response depending on what the message type is
if (msg[2] === "BootNotification") {
//Send correct response
} // Add all the message types
});
});
With this I get the message type printed to the console as a string:
Message type: BootNotification
So my question is that is this the correct way to get the type of the message?
I am new to this so I want to make sure.
The specification for OCPP 1.6 JSON is available here: OpenChargeAlliance website
I guess YES. JSON.parse is the built-in to, well, pares JSON strings. In case that goes wrong it throws an error, so you might try/catch this.
Since the response you get is an array, there is no other way as to access its items with a numeric index.
In such cases I personally prefer to have something like that:
const handlers = {
'BootNotification': request => { 'msg': 'what a request' }
};
Than you can:
let respone = {'msg': 'Cannot handle this'}
if (handlers.hasOwnProperty(msg[2])) {
response = handlers[msg[2]](msg);
}
But that is just the way I would go.
If you are asking about OCPP message structure (not parsing a JSON), I can provide you the details about OCPP 1.6 version.
In OCPP 1.6, the client (Charging Station) sends a CALL (similar to request in HTTP) to server (Charging Station Management Systems). All CALLs have a strict structure of 4 elements:
MessageTypeId (integer)
UniqueId (UUID, string)
Action (string)
Payload (JSON object containing the arguments relevant to the Action.)
or as in your example:
[
2,
'bc7MRxWrWFnfQzepuhKSsevqXEqheQSqMcu3',
'BootNotification',
{ chargePointVendor: 'AVT-Company',
chargePointModel: 'AVT-Express',
chargePointSerialNumber: 'avt.001.13.1',
chargeBoxSerialNumber: 'avt.001.13.1.01',
firmwareVersion: '0.9.87',
iccid: '',
imsi: '',
meterType: 'AVT NQC-ACDC',
meterSerialNumber: 'avt.001.13.1.01' }
]
So the Type of Action should be always at index of 2 (as you retrieve it when you parse received message). You can refer to #philipp anwser on way how to handle an errors when parsing.
I need to get number of items of specific directory in Node.js
If I get the items like
var dirItems = fs.readdirSync(__dirname+'/my_dir');
and then get specific item like
dirItems[1]
everything is ok
But if I try to get their number like
dirItems.length
or
Object.keys(dirItems).length
the page doesn't work in the browser
How to get the number of directory items?
UPDATED
My full code:
var http = require('http'),
fs = require('fs');
http.createServer(function(req, res) {
var dirItems = fs.readdirSync(__dirname+'/my_dir');
res.writeHead(200, {'Content-Type': 'text/html'});
res.end(dirItems.length);
}).listen(80, 'localhost');
I was able to reproduce the error nyou get.
res.end() for the basic http server class is very picky about what you send it. You must give it a string (the error you got should have been a big clue here).
So, change this:
res.end(dirItems.length);
to this:
res.end(dirItems.length.toString());
And, it works for me. I was able to reproduce your original error and then make it work by making this simple change.
Logically, you can only send string data as an http response so apparently res.end() isn't smart enough to attempt a string conversion on its own. You have to do it yourself.
FYI, if you use a higher level framework like Express, it is more tolerant of what you send it (it will attempt a string conversion in a situation like this).
Here is how I would do it:
const fs = require('fs');
const dir = './somedir';
fs.readdir(dir, (err, files) => {
console.log(files.length);
});
To keep things clean in my express route page I have a local function that is called in every route and it passes the sql query together with the req and res objects.
This works fine for sending a successful result and calling res.send works.
The problem that I'm having is I can't seem to find a way to get res.status to work and no matter the syntax it simply times-out and gives no error whatsoever in the console OR on the front end.
The tricky thing is, when it's inside the specific route it does work but the error message does not seem to get sent through instead it's just blank body?
`async function queryDatabase(queryParam, req, res) {
try {
const cp = new sql.ConnectionPool(config);
await cp.connect();
let result = await cp.request().query(queryParam);
cp.close();
res.send(result.recordset);
} catch (err) {
res.statusMessage = `Database error: ${err}`;
res.status(520);
}
}`
res.status(520) only sets the status value in the response object. It does not actually send the response. So, to send the response, you have several options. In the more recent versions of Express, you can use this shortcut:
res.sendStatus(520);
This will both set the status and send the response.
But, you can also do this in any version of Express:
res.status(520).end();
Which also sets the status and then sends the response.
You should end your response, use res.status(520).end() instead of res.status(520)
I have a problem where request.body.email returns me undefined.
I wrote this code on my controller on my client side:
wish.controller('wishCtrl',['$scope','$http','$cookies',function($scope,$http,$cookies) {
var user={};
user.email = $cookies.get('cookieEmail');
console.log(user.email);
$http.get("http://localhost:3000/wishlist",user).success(function(data){
$scope.wishController = data;
console.log(data);
});
}]);
here I see - user.email ok so there is no problem here.
on my controller on my server side I wrote:
exports.getData = function(request, response) {
userEmail = request.body.email;
console.log(userEmail);
}
which writes me back undefined.
to call this function I have on my server.js (on the server side)
app.get('/wishlist',wish.getData);
any idea how to fix it?
You are making a GET request. There is no request body in a GET request.
If you want to read query string data then parse request.url.
The Angular documentation for get says that the last argument must be a configuration object. So it looks like you aren't even managing to put your data in the URL either. Pass a configuration too.
$http.get("http://localhost:3000/wishlist",user, {})
because i't get function have to pass the email on the client side this way:
$http.get("http://localhost:3000/wishlist/"+user.email)
and the path of the sever should recognize it that way:
app.get('/wishlist/:email',wish.getData);
and int the controller that way:
userEmail = request.params.email;
console.log(userEmail);