Develop Reference

Accessing local json files from the browser using NodeJs backend

I am working on a react application that takes the json file path as a parameter to render the json data in my ui. Accessing local files from the browser is restricted, so how can I create a backend server to retrieve my local json files and serve them to the browser?

you can boot up a local server using express, and use the fs module to access file content
const fs = require('fs');
const file_content = fs.readFileSync('./{file_name}',
'{content_formate}').toString();
// For show the data on console
console.log(file_content);
To create a server that is listening on port 3000, use
const express = require('express')
const fs = require('fs');
const app = express()
const port = 3000
app.get('/', (req, res) => {
const file_content = fs.readFileSync('./{file_name}',
'{content_formate}').toString();
res.send(file_content)
})
app.listen(port, () => {
console.log(`Example app listening at http://localhost:${port}`)
})
something like this

To access local json files in your swagger application, you need to use express - as the browser cannot access your local file system. You can create an endpoint, i.e. '/swagger', that will allow you to serve the files from the directory provided. In the urls parameter, you will use '/swagger/name.json', rather than the local path. Create a driver.js file with the following content:
var express = require('express');
var app = express();
app.use('/swagger', express.static('/path/to/local/files'));
app.listen(3000);

Save JSON data from an API into a database and cache the request, so i won't need to request from the API again - Node.js / Express.js

I have this URL here: https://viacep.com.br/ws/01001000/json/ , that lets me retrieve JSON data whenever i change the given number on it(the number is unique). For example: 01001000 has its own data, and if i change it for 49140000, it will have its own data as well. What i want to do is: i want to save the JSON data into a database, and somehow cache/save the request, so if in the future i search for the same number again, it won't have to retrieve the data from the URL again.
I have this right now:
My city.routes.js where i make the request to the API:
const express = require('express');
const axios = require('axios');
const cityRouter = express.Router();
cityRouter.get('/:cep', async (request, response) => {
try {
const { cep } = request.params;
const resp = await axios.get(`https://viacep.com.br/ws/${cep}/json/`);
return response.json(resp.data);
} catch (error) {
return response.status(400);
}
});
module.exports = cityRouter;
An index.js to make easier to the server to import and use the routes:
const express = require('express');
const routes = express.Router();
const cityRoutes = require('./city.routes');
routes.use(cityRoutes);
module.exports = routes;
My server.js:
const express = require('express');
const routes = require('./routes');
const app = express();
app.use(express.json());
app.use(routes);
app.listen(3333, () => {
console.log('Server is on!');
});
I can retrieve the JSON data that i want without problems:
enter image description here

You can do this via using caching libraries or using db and indexing on based of number for faster retrieval.
My suggestion:
If you need to cache for smaller amount of time lets say week or so prefer caching libraries like redis or memcache.
There u can do something like:
await redis.set(key, JSON.stringify(data), { expiry: '1W'});
The above code varies depending on library you use. But the idea remains the same you cache the data with key(Number).
And next time before making request you first tries to get the key from cache provider.
await redis.get(key)
if above value is present you will get json string of the desired result and dont need to make the network call.
If not present you make the network call and cache the result for future use.
In case of DB approach you simply make a get request via key to the db.
But do index the key in collection or relation when initializing the structure for faster retrieval.

why my fetch post is not working it is not responding?

addwordform.addEventListener('submit', (event)=>{
event.preventDefault();
const formdata=new FormData(addwordform);
const word=formdata.get('addword');
const description =formdata.get('addiscription');
const worddata={
word,description,totalcount
};
console.log(worddata);
fetch(API_URL,{
method:'POST',
headers:{
'content-Type':'application/json'
},
body:JSON.stringify(worddata),
}).then(response=>response.json()).then( data =>{
console.log(data);
});
});
this is the client side javascript
here API_URL="http://localhost:3005/word"
and server side code is
const express= require('express');
const serveStatic = require('serve-static');
const datastore= require('nedb');
const app= express();
app.listen(3005,()=>{console.log("listening on :http://localhost:3005")});
app.use(serveStatic('public',{'index':['client.html']}));
const database=new datastore('database.db');
database.loadDatabase();
app.post('/word',(req,res)=>{
const data=req.body;
database.insert(data);
res.json();
});
i am using express a node framework and vanilla javascript for client side all i want is to post the data from a form that has an id=addwordform and i am using nedb a light weight database management in node
.problem with it is the worddata that i am sending from client side is not getting in the server side "req" so i cant save it in database and ultimatly i cant "res" it back ?

If you're using express version >= 4.16. Body parser comes bundled with express.
It parses incoming requests with JSON payloads and is based on body-parser.
It is not needed to use body-parser. Here is the documentation
You just have to add this code before require your routes.
app.use(express.json());
Here is the stackoverflow original post.
Here is the express release
Here is the express commit

How to properly access the app variable set by express in a node.js app?

I'm building a node.js server and my folder structure looks like this:
server.js
app/routes.js
app/routes/users.js
My problem is that i'm not sure how can i use the app variable inside the users.js file. Do i have to require and setup express again in this file or is there a better/easier way to do it? Here is my sample code(just the bare minimum to understand my problem):
server.js
// Include our packages in our main server file
var express = require('express');
var stormpath = require('express-stormpath');
var app = express();
// Init Stormpath for user management and authentication
app.use(stormpath.init(app));
// Load routes
require('./app/routes')(app);
// Start the server
app.listen(process.env.PORT);
// Stormpath will let you know when it's ready to start authenticating users.
app.on('stormpath.ready', function () {
console.log('Your server is running on port ' + port + '.');
});
app/routes.js
// Import dependencies
const express = require('express');
const stormpath = require('express-stormpath');
// Export the routes for our app to use
module.exports = function(app) {
// Create API group routes
const apiRoutes = express.Router();
// User management: get users, invite users, view user profile
var UsersRoute = require('./routes/users');
apiRoutes.get('/memberinfo', stormpath.loginRequired, UsersRoute.memberInfo);
// Set url for API group routes
app.use('/', apiRoutes);
};
app/routes/users.js
// Protected route test
module.exports.memberInfo = function(req, res){
//how do i access the "app" here?
res.status(200).send({ user: req.user });
}

In your .memberInfo method, you can use req.app to access the app object that is associated with that request.
In cases where you aren't passed a req object that you can use in this way, then you need to initialize the module by calling a method on it and passing it the app object and the module can then store the app object locally so it can use it when desired.

Nodejs, expressjs - how to serve delayed response

I am building a webservice, for which i am using nodejs, phantomjs and expressjs. I am learning all the three.
I want to serve a delayed response to the clients after processing their query. Like for example,
I am processing certain inputs from my client, then, i want to process the data at the backend which will take approx 10 sec on an avg. Then i wanted to serve this page to the client.
Is it possible in node to send multiple responses to the same request or delayed responses so that the template will automatically update the contents.
Or , should i use the same method , like store the json in a file in the server , then serve the page with ajax which will query the page.
please help me. here is the code which i wrote ,
app-server.js(the main file):
// import express module
var express = require('express');
var bodyParser = require('body-parser');
var app = express();
// define all required template files to be served and also define the template engine
app.engine('.html', require('ejs').__express);
app.set('views', __dirname + '/views');
app.set('view engine', 'html');
// Useful modules
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({extended: true}));
// import the routes
require('./router')(app);
app.listen(8080);
router.js:
var crypto = require('crypto');
var express = require('express');
module.exports = function (app) {
// define the static routes.
app.use('/static', express.static('./static'));
app.use('/media', express.static('./media'));
//defining the controller.
var parserlib = require('./controller.js')
// Define the home root path
app.get('/', function (req, res) {
// shows the home search page.
res.render('index', {content:'template success'});
});
app.get('/search', function(req, res){
res.redirect('/');
});
app.post('/search', parserlib.parserlib);
}
controller.js:
var crypto = require('crypto');
var path = require('path')
var childProcess = require('child_process')
exports.parserlib= function(req, res){
var output = '';
var url = req.body.search_url;
var childArgs = [
path.join(__dirname, 'external-script.js'),
url,
]
// execute the script in a separate thread.
childProcess.execFile(binPath, childArgs, function(err, stdout, stderr) {
// handle results
console.log(stdout);
output = stdout;
//console.log(err);
//res.send(output);
});
//res.send(output);
};
so , what i want to see is, first send a response to client stating that its loading, then i want to update the with processed data. In other languages its not possible to send multiple responses. Not sure about nodejs.
Also, do i have to store the json output from the processed lib to a file and then use ajax to query ? or is it possible to directly update the json object to the client ?
Thanks

This is just not how HTTP works. The clients won't expect it. This has nothing to do with Node or any other framework. The way to do what you're attempting is to actually send a response that the thing is loading, and then have some other mechanism for reporting state.
As an example, you might design a RESTful API. In that RESTful API you might define a endpoint for creating new things:
POST /api/things
The client would post data to that to create a new thing. The response should be something that provides a location of the newly created resource, for example an HTTP 301 to /api/things/1.
If the user goes to /api/things/1 and the thing isn't done getting made yet, then you can either do a temporary redirect (303) to /api/things/1/status which provides some helpful status information, or just issue a 404.
If you actually want to send back server-side pushes of status information, then you should be looking at WebSockets or a pure Socket API of some kind, neither of which is provided by Express, but both of which are available in Node (checkout the socket.io library and the net core library)