Develop Reference

Getting Console Messages on Webpage NodeJS

I'm wondering if there's any way to listen for console messages and act on console messages when they're received. Mainly, is there any way to do this without an external module, and using the http module?
The goal is to trigger a NodeJS function or code snippet on an event like click in the HTML. If there's also a way to do this, then that's great. But once again, I'd like to do this without an external module, and just use those that are built-in to NodeJS.

Use onclick() function in JavaScript to trigger a function call when clicking on a element. Then use fetch to make a api call to the nodejs server.

I know #Haris Wilson already got the answer, but I'd just like to provide a code example.
Instead of trying to catch a console message and then execute a function if we find it, we can use fetch() to make a request to whatever URL we need, and this can allow us to make other requests.
In this case, we can use the url module and the http module to parse the url and serve the API and website, respectively.
const url = require('url')
const http = require('http')
const requestListener = async function (req, res) {
// Basic server setup
res.writeHead(200, {
'Content-Type': 'text/html'
});
res.end(/** Content here */)
// API
if (url.parse(req.url, true).pathname === '/APIcall') {
let arguments = url.parse(req.url, true).query
// Preform necassary actions here
}
}
We can now use onClick to call a function inside our webpage JavaScript, and use fetch([API URL]) to give our NodeJS data to preform an action. We can use URL params to do this, such as https://localhost:8080/APIcall?data=someData&moreParam=more-data, where ?data=someData&moreParam=more-data are the URL params.

Using a global translation object in express JS

I've built a very simple translation module for Express JS, it's a global object in the application scope that's instantiated at application runtime:
translator.configure({
translations: 'translations.json'
});
I've added some simple middleware to Express JS that changes the locale in the translator module for each request:
app.use(function(req, res, next) {
var locale = // Get locale from request host header
// Setup the translator
translator.setLocale(locale);
// Attach translator to request parameters
res.locals.__ = translator.translations;
// Pass control to the next middleware function
next();
});
Then I access my translations through the variable __ in my views (here I use ejs):
...
Here is my translated text: <%= __['test'] %>
...
My translator module looks like this:
var translations,
locale;
// public exports
var translator = exports;
translator.configure = function(opt) {
translations = require('./' + opt.translations);
};
translator.setLocale = function(locale) {
translator.translations = translations[locale];
}
The translations.json file is just a simple JSON structure:
{
"us":{
"test": "Hello!"
},
"es":{
"test": "Hola!"
}
}
My question is, is this overall structure a bad idea? I do not have extensive knowledge about express JS. The global object makes me kind of nervous since the translations are based of its current state, which is changed from request to request, any problems here? Does express JS fully complete a request before handling the next one, or is there some level of concurrency going on that can mess up my translations?

A global object is a bad idea for saving state that is used during a request. A request is not necessarily completed before the next one starts running. If, at any time, a request handler makes an asynchronous call (like to read a file), then another request can start running at that point.
In general, you should store state related to a specific request on the request object itself. That way, it is not global and is stored specifically for that request only and you can have as many requests going at once without conflict.
So, you could ideally not store any request-specific state in your translator object at all unless you create a new translator object for each request and then store that specific translator object in the request object.
I don't follow your translator code exactly, but this looks like trouble:
app.use(function(req, res, next) {
var locale = // Get locale from request host header
// Setup the translator
translator.setLocale(locale);
// Attach translator to request parameters
res.locals.__ = translator.translations;
// Pass control to the next middleware function
next();
});
Because it looks like you're configuring a shared, global translator object, then expecting to use it later and expecting it not to be changed by any other request. That seems like asking for trouble.
If your request handler makes any async call at any point, then another request handler can run which can create a conflict as both try to use the same translator object.

How to pass request parameters back to Angular

I currently have an app which uses Express with Jade templates.
I'm building a new version of the app using Angular with client-side HTML.
I need access to certain request parameters in order to determine user permissions in my Angular code. My problem is that I don't know how to get ahold of these parameters in my Angular controllers/services.
Below is what currently occurs in Express with the Jade structure:
routes.js:
router.get('/player/:id',
playerRoute.show
);
player.js:
var show = function(req, res) {
res.render('player', {user: req.user});
};
...and now my new version's handler:
var player = function(req, res) {
//res.sendFile(path.join(__dirname, '../v2', 'index.html'));
res.json({user: req.user});
};
The correct user JSON is sent back to my client-side with the code above. When res.json is commented out and res.sendFile uncommented the correct HTML is rendered. My dilemma is how to both render this HTML AND provide my client-side Angular code with the user JSON object?

After all that, your question just boils down to:
MY dilemma is how to both render this HTML AND provide my client-side Angular code with the user JSON object?
You don't. The usual case is to just render the HTML along with the assets needed to render the initial app (hide everything, show a splash screen whatever). Further data (like getting your user) is handled by API calls to your server via Angular's HTTP facilities. That means they are separate. After that API call, your app determines what to render.
Otherwise, you could just render the data in the HTML as some global variable and have Angular pick it up from there. This is messy IMO, but doesn't require a separate API call to get the data.

copied from my own answer to a similar question
To get a variable from server to client javascript try templating a json string into the html and loading it from the javascript. EJS handles quote escaping and I think Jade does too. For reference content!= safeString tells Jade to skip escaping, so does content !{safeString}.
- var user={id:1, displayName:'foo'}
#example
meta(data-userJSON=JSON.stringify(user))
script(src="//code.jquery.com/jquery-1.11.3.min.js")
script.
var user = JSON.parse(
$('#example meta').attr('data-userJSON')
)
console.log(user);
span #{user.id}
span #{user.displayName}

Here's how I ended up handling this situation. I simply created a new API endpoint which I can easily hit with an Angular service. Here's the Node setup:
routes.js:
router.get('/currentUser',
apiController.currentUser.index
);
currentUser.js:
var index = function(req, res) {
res.json({user: req.user});
};
module.exports = {
index: index
};
Still seems odd to me to make an API call to get the request parameters, but it works. Feedback appreciated.

Rewrite URL in AngularJS Factory

The app I'm developing allows users to change the IP of the server (where the REST API is). This address is stored in a variable that can change, but the problem is that when the services are instantiated, the base URL cannot be changed. Following this answer I was able to change the url of some of the services, but I can't do the same for those who have POST actions.
I've tried several configurations, but there's always a problem. For example, this:
// Services file
app.factory('Bookings', BookingsFactory)
function BookingsFactory($resource, GlobalVariables) {
return $resource('http://:url/api/bookings/:id/', null, {url: '#url'});
}
//Controllers file
Bookings.save(booking, {url: GlobalVariables.IPServer});
Throws this error message "net::ERR_NAME_NOT_RESOLVED", because the request URL is not correct: "http://api/bookings/?end_time=2015-06-30T09:30&name=Reunion&room=1&start_time=2015-06-30T09:43&started=true".
If I call it like this:
//Services file
app.factory('Bookings', BookingsFactory)
function BookingsFactory($resource, GlobalVariables) {
return $resource('http://:url/api/bookings/:id/', {url: '#url'});
}
//Controllers file
Bookings.save({booking: booking, url: GlobalVariables.IPServer});
I get a 400 BAD REQUEST error, and the response asks for content for all the required fields: "This field is required."
I'm using AngularJS v1.3.13. Is there a way to change the base URL in every petition with this approach, even on POST requests? Or even better, is there a way to update the URL in every factory of the application after the app is started?

In an app that I work on I use the $rootScope to hold my base server URL for all requests. I don't know if that's a good way to use $rootScope or not, but what's for sure is that the app is working.
oops sorry I forgot to also add that I can change the base URL while the app is running, which is what you need.

Basic Ajax send/receive with node.js

So I'm trying to make a very basic node.js server that with take in a request for a string, randomly select one from an array and return the selected string. Unfortunately I'm running into a few problems.
Here's the front end:
function newGame()
{
guessCnt=0;
guess="";
server();
displayHash();
displayGuessStr();
displayGuessCnt();
}
function server()
{
xmlhttp = new XMLHttpRequest();
xmlhttp.open("GET","server.js", true);
xmlhttp.send();
string=xmlhttp.responseText;
}
This should send the request to server.js:
var http = require('http');
var choices=["hello world", "goodbye world"];
console.log("server initialized");
http.createServer(function(request, response)
{
console.log("request recieved");
var string = choices[Math.floor(Math.random()*choices.length)];
console.log("string '" + string + "' chosen");
response.on(string);
console.log("string sent");
}).listen(8001);
So clearly there are several things going wrong here:
I get the feeling the way I am "connecting" these two files isn't correct both in the xmlhttp.open method and in using response.on to send the string back to the front end.
I'm a little confused with how I call this page on localhost. The front end is named index.html and the sever posts to 8001. What address should I be go to on localhost in order to access the initial html page after I have initialized server.js? Should I change it to .listen(index.html) or something like that?
are there other obvious problems with how I am implementing this (using .responsetext etc.)
(sorry for the long multi-question post but the various tutorials and the node.js source all assume that the user already has an understanding of these things.)

Your request should be to the server, NOT the server.js file which instantiates it. So, the request should look something like this: xmlhttp.open("GET","http://localhost:8001/", true); Also, you are trying to serve the front-end (index.html) AND serve AJAX requests at the same URI. To accomplish this, you are going to have to introduce logic to your server.js that will differentiate between your AJAX requests and a normal http access request. To do this, you'll want to either introduce GET/POST data (i.e. call http://localhost:8001/?getstring=true) or use a different path for your AJAX requests (i.e. call http://localhost:8001/getstring). On the server end then, you'll need to examine the request object to determine what to write on the response. For the latter option, you need to use the 'url' module to parse the request.
You are correctly calling listen() but incorrectly writing the response. First of all, if you wish to serve index.html when navigating to http://localhost:8001/, you need to write the contents of the file to the response using response.write() or response.end(). First, you need to include fs=require('fs') to get access to the filesystem. Then, you need to actually serve the file.
XMLHttpRequest needs a callback function specified if you use it asynchronously (third parameter = true, as you have done) AND want to do something with the response. The way you have it now, string will be undefined (or perhaps null), because that line will execute before the AJAX request is complete (i.e. the responseText is still empty). If you use it synchronously (third parameter = false), you can write inline code as you have done. This is not recommended as it locks the browser during the request. Asynchronous operation is usually used with the onreadystatechange function, which can handle the response once it is complete. You need to learn the basics of XMLHttpRequest. Start here.
Here is a simple implementation that incorporates all of the above:
server.js:
var http = require('http'),
fs = require('fs'),
url = require('url'),
choices = ["hello world", "goodbye world"];
http.createServer(function(request, response){
var path = url.parse(request.url).pathname;
if(path=="/getstring"){
console.log("request recieved");
var string = choices[Math.floor(Math.random()*choices.length)];
console.log("string '" + string + "' chosen");
response.writeHead(200, {"Content-Type": "text/plain"});
response.end(string);
console.log("string sent");
}else{
fs.readFile('./index.html', function(err, file) {
if(err) {
// write an error response or nothing here
return;
}
response.writeHead(200, { 'Content-Type': 'text/html' });
response.end(file, "utf-8");
});
}
}).listen(8001);
console.log("server initialized");
frontend (part of index.html):
function newGame()
{
guessCnt=0;
guess="";
server();
displayHash();
displayGuessStr();
displayGuessCnt();
}
function server()
{
xmlhttp = new XMLHttpRequest();
xmlhttp.open("GET","http://localhost:8001/getstring", true);
xmlhttp.onreadystatechange=function(){
if (xmlhttp.readyState==4 && xmlhttp.status==200){
string=xmlhttp.responseText;
}
}
xmlhttp.send();
}
You will need to be comfortable with AJAX. Use the mozilla learning center to learn about XMLHttpRequest. After you can use the basic XHR object, you will most likely want to use a good AJAX library instead of manually writing cross-browser AJAX requests (for example, in IE you'll need to use an ActiveXObject instead of XHR). The AJAX in jQuery is excellent, but if you don't need everything else jQuery offers, find a good AJAX library here: http://microjs.com/. You will also need to get comfy with the node.js docs, found here. Search http://google.com for some good node.js server and static file server tutorials. http://nodetuts.com is a good place to start.
UPDATE: I have changed response.sendHeader() to the new response.writeHead() in the code above !!!

Express makes this kind of stuff really intuitive. The syntax looks like below :
var app = require('express').createServer();
app.get("/string", function(req, res) {
var strings = ["rad", "bla", "ska"]
var n = Math.floor(Math.random() * strings.length)
res.send(strings[n])
})
app.listen(8001)
https://expressjs.com
If you're using jQuery on the client side you can do something like this:
$.get("/string", function(string) {
alert(string)
})

I was facing following error with code (nodejs 0.10.13), provided by ampersand:
origin is not allowed by access-control-allow-origin
Issue was resolved changing
response.writeHead(200, {"Content-Type": "text/plain"});
to
response.writeHead(200, {
'Content-Type': 'text/html',
'Access-Control-Allow-Origin' : '*'});

Here is a fully functional example of what you are trying to accomplish. I created the example inside of hyperdev rather than jsFiddle so that you could see the server-side and client-side code.
View Code:
https://hyperdev.com/#!/project/destiny-authorization
View Working Application: https://destiny-authorization.hyperdev.space/
This code creates a handler for a get request that returns a random string:
app.get("/string", function(req, res) {
var strings = ["string1", "string2", "string3"]
var n = Math.floor(Math.random() * strings.length)
res.send(strings[n])
});
This jQuery code then makes the ajax request and receives the random string from the server.
$.get("/string", function(string) {
$('#txtString').val(string);
});
Note that this example is based on code from Jamund Ferguson's answer so if you find this useful be sure to upvote him as well. I just thought this example would help you to see how everything fits together.