node.js how to respond .js files with parameters - javascript

I have a node.js http application and i'm servicing GET requests ok. I can't however respond properly with requests for say foo.js?_param=1234. How do i deal correctly with files of this type where parameters are being passed?
EDIT:
I'm using express to service files as follows:
app.get('/*', function(req, res) {
res.sendfile(__application+req.url, {root: __root});
});
__root is the root path of the application.

Use request.url, it will look like /foo.js?_param=123.
Then use require('url').parse(url,true) to split this into meaningful parts (true is to also expand individual query string parameters).
See http://nodejs.org/api/http.html#http_request_url for details.

Try using the express module.
They have a whole API for dealing with GET and POST requests.
You can use req.query to handle the get requests.

Related

Using Node.js to access data from a running executable program

I have a large program written in C# using Visual Studio that is running as a standalone executable complete with an extensive GUI interface. We want to add a web interface to the program in order to get most, if not all of the functionality available.
The first step I took was to add a web server to the C# executable and I linked in some web pages (html and css) and I was able to present some data as a test case and this worked.
We decided that it would be better to treat the standalone executable like a database where we would prefer to send requests to the get data and post data to store data.
I'm using Node.js framework and Express as my webserver. I have a number of web pages designed and I'm using javascript and some embedded javascript to render data on some of the web pages.
The issue I'm having is how do I process a selected route on one of my webpages to force the the .js file that is processing the route to go out and access the executable program that is running on the same computer at this moment to both get and set data in the executable program and then present it back on the web page.
HTML code (test_data_02.ejs)
<input class="LSNButton1" type="button" style="color:black; background:green;" value="Test Button B" onclick="window.location.href = '/get_test_02b'" />
Javascript (Express) (main.js)
const { json } = require("express");
const express = require("express"),
app = express(),
fs = require("fs"),
homeController = require("./controllers/homeController"),
errorController = require("./controllers/errorController"),
data_entry_03 = require("./public/js/data_entry_03"),
layouts = require("express-ejs-layouts");
app.set("view engine", "ejs");
app.use(layouts);
app.use(express.static("public")); //tell the application to use the corresponding public folder to serve static files
app.use(express.urlencoded({ //assists in reading body contents, parse incoming requests in url format
extended: false
}));
app.use(express.json()); //assists in reading body contents, parse incoming requests in json format
app.set("port", process.env.PORT || 3000);
console.log("MAIN MAIN MAIN"); //this only happens once on start up - this file is only executed on startup, everything is configured on startup
//MIDDLEWARE CODE
app.use((req, res, next) => { //this is a generic middleware function that will be called before any route is processed
homeController.middleWareFunction(req, res); //process this function before moving on to next route that was selected
//console.log(req.query); //from the browser: http://localhost:3000?cart3&jack=5, this results in a request to /?cart=3&jack=5, how do i make a post for this
console.log(`request made to: ${req.url}`);
console.log("");
next();
})
//app.use("/general_data", homeController.readDataFile); //run this function for every request made to the path beginning with this route - it does not imply it is a middleware that will run on this route before the get
//GET ROUTE CODE
app.get("/", homeController.showHome); //a specific route has been identified and the callback function assoicated with the particular route is specified
app.get("/specific_data", homeController.showSpecificData);
app.get("/general_data", homeController.showGeneralData);
app.get("/get_test_02b", homeController.getTest02B);
More Javascript (homeController.js)
I was hoping somewhere in 'getTest02B' or in 'getTestData02B' I would be able to send or request data from the executable program somehow. Maybe using a URL. I would obviously need to add code to my executable to process the requests to either send or receive data. I would like to be able to process the data as JSON, XML, or text data in both directions. I just can't see the mechanism to perform this operation.
exports.getTest02B = (req, res) => {
console.log("in exports.getTest02B");
displayInformation(req.url, "URL");
displayInformation(req.method, "METHOD");
displayEmptyLine();
getTestData02B(function (err, data) {
if (err)
return res.send(err);
res.send(data);
});
};
One comment on this issue was that I needed to make a http request to the C#
program. I understand that Node.js allows several connections per server to
make HTTP requests.
I'm using the code below and it is not working.
const req = http.request('http://192.168.1.222/ListAlarms.html', (res) => {
console.log('STATUS:${res.statusCode}');
});
req.end;
When I run this code there appears to be no response from the C# program.
From the editing environment where I wrote the code above, if I select the URL and press CONTROL and CLICK I end up launching another browser with the data being displayed because the C# program is currently running. This implies to me that at least the URL in the http.request statement is good. Just to confirm the URL was working I ran the C# program in the debugger and I was able to break on receiving the URL. The URL is good but I just can't seem to access the C# program from the Node.js environment using the same URL. Obviously I'm doing something wrong.
I assume that once I'm able to generate a http.request from the Node.js environment I would be able to control the flow of data to and from the C# program.
Any input would be appreciated.

How to access POST data in express js?

Im using (in the browser):
xmlHttp.open("POST", "/", true); // true for asynchronous
xmlHttp.send("data");
on the client side browser.
I'm using (node js):
app.post("/", function (req, res) {
console.log("Got a POST request");
console.log(req);
});
to get the post data. but it doesn't matter what I send it doesn't show up.
I don't wanna have to install some separate "body parser" package to see the data.... I don't wanna parse it. A post request is used to send data to the server... is the data just not there?
I don't wanna have to install some separate "body parser" package to see the data.... I don't wanna parse it.
Too bad.
Even if you want to process a plain text body then you need to use body parsing middleware to do it.
One of the responsibilities of the middleware is to take the stream of data from the client and store it in memory (assigning it to req.body) instead of discarding it.
Note that body parsing middleware is installed automatically as a dependency of Express.js itself.
There is no need for a separate body parser library. You can use express.json. It
is a built-in middleware function in Express. You can use it like:
app.use(express.json())
You can read more about it here.

Difference between request and query?

I'm learning a bit of Javascript and mongodb , actually i installed ExpressJS which have .request , and QueryStringParser modulles which have .query . Which is the difference between both?
You don't say which QueryStringParser modules did you installed, but since you already mention MongoDB I assume you are talking about this https://github.com/diegohaz/querymen
Expres request handles the HTTP requests while Querymen's query is an Express middleware to build a MongoDB query from parameters in the HTTP querystring request nothing else.
You can read more about both in the following links
https://expressjs.com/en/api.html#req
https://github.com/diegohaz/querymen

Send JSON data from express to html NodeJS

Hello all i'm new with node so here my use case i want to post data to my express app and show it on a html page is that possible with nodeJs ?
Here my code
app.post('/', function(req, res){
res.sendFile(__dirname + '/views/index.html', {data: req.body});
})
There are many tutorials showing how to do that. I would recommend first you understand how HTTP protocol works (The message structure : https://www.w3.org/Protocols/rfc2616/rfc2616-sec4.html). Then go dive into node and exchange data through requests and responses. I'd recommend body-parser to arrange the data format between the two sides. Also read the express documentation. Hope it helps.

Communication between an express node server and its displaying html

Really fast, this question may have already been asked, but I am not totally clear on the terminology and have had no success when searching for a solution.
I am attempting to create a simple web application that can receive get and post requests. Then, I would like to take the information I receive from these requests and use them in a javascript file embedded in html that is displayed. I think it may be more clear with code. This is my app.js:
var express = require('express');
var app = express();
var assert = require('assert');
app.use(express.static('javascript'));
app.get('/', function(req, res) {
res.render('index.jade');
});
app.listen(3000);
I would then like to be able to take information received from a get or post request, specifically in JSON format, and then be able to use it in javascript that I have linked to index.jade. To make matters slightly more confusing in index.jade the only line is:
include map.html
So ideally I would be able to get the information to javascript in that html file.
I want to be able to pretty continuously update map.html using javascript based on frequent get and post commands.
This could be a very simple solution, I am pretty new with web application programming in general, and I have been struggling with this problem. Thanks in advance, and ask if you need any clarification.
I think you need to understand what you are doing. You are creating a web server using node.js. Express framework simplifies that for you. The official documentation of express is pretty great. You should refer that especially this link.
Now, in your application, you need to create endpoints for GET and POST requests. You have already created one endpoint "/" (root location) that loads your home page which is the contents of the file index.jade. A small example is :
app.get('/json', function (req, res) {
res.setHeader('Content-Type', 'application/json');
res.send(JSON.stringify({ a: 1 }));
});
Jade is a templating engine which resolves to HTML. You should refer its documentation as well. Since as you said, you are not very familiar with these, you could simply use HTML as well.
After this tasks are quite simple. In your javascript, using ajax calls you can access the GET or POST endpoints of your server and do the desired actions.
Hope it helps!
The way I get it you want to be able to call an endpoint (lets assume /awesome) pass some info and then write to a Javascript file that you can then reference in your html.
Something like the below would write a main.js file in your public folder. You can make it write whatever you want.
var fs = require('fs');
fs.writeFile("/public/main.js", "console.log('Hello!')", function(err) {
if(err) {
return console.log(err);
}
console.log("The file was saved!");
});
You can then reference /public/main.js in your html.
Check that: Writing files in Node.js
If I misunderstood your intentions, apologies. :)
So you want to reviece continuously data from the server maybe web sockts are an option for you http://socket.io/docs/
This way u will open a stable connection from the client to the server. This is a great way if u want to get updates done by other clients.
If you want to trigger the changes by the client then ajaxs calls(http://www.w3schools.com/ajax/) as hkasera mentioned are the way to go.

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