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web scraping for html page but need for repeat on lots link?

I wrote the following code for parse some part of HTML for one URL. I means parse page const URL= 'https://www.example.com/1'
Now I want to parse the next page 'https://www.example.com/2' and so on. so I want to implement a For-Loop manner here.
what is the easiest way that I can use the iteration manner here to
change URL (cover page 1,2,3, ...) automatically and run this code in repeat to parse other pages? How I can use for-loop manner here?
const PORT = 8000
const axios = require('axios')
const cheerio = require('cheerio')
const express = require('express')
const app = express()
const cors = require('cors')
app.use(cors())
const url = 'https://www.example.com/1'
app.get('/', function (req, res) {
res.json('This is my parser')
})
app.get('/results', (req, res) => {
axios(url)
.then(response => {
const html = response.data
const $ = cheerio.load(html)
const articles = []
$('.fc-item__title', html).each(function () {
const title = $(this).text()
const url = $(this).find('a').attr('href')
articles.push({
title,
url
})
})
res.json(articles)
}).catch(err => console.log(err))
})
app.listen(PORT, () => console.log(`server running on PORT ${PORT}`))

Some considerations, if you added CORS to your app, so that you can GET the data, it's useless, you add CORS when you want to SEND data, when your app is going to receive requests, CORS enable other people to use your app, it's useless then trying to use other people's app. And CORS problems happen only in the browser, as node is on the server, it will never get CORS error.
The first problem with your code, is that https://www.example.com/1, even working on the browser, returns 404 Not Found Error to axios, because this page really doesn't exist, only https://www.example.com would work.
I added an example using the comic site https://xkcd.com/ that accepts pages.
I added each axios request to an array of promises, then used Promise.all to wait for all of them:
The code is to get the image link:
const PORT = 8000;
const axios = require("axios");
const cheerio = require("cheerio");
const express = require("express");
const app = express();
const url = "https://xkcd.com/";
app.get("/", function (req, res) {
res.json("This is my parser");
});
let pagesToScrap = 50;
app.get("/results", (req, res) => {
const promisesArray = [];
for (let pageNumber = 1; pageNumber <= pagesToScrap; pageNumber++) {
let promise = new Promise((resolve, reject) => {
axios(url + pageNumber)
.then((response) => {
const $ = cheerio.load(response.data);
let result = $("#transcript").prev().html();
resolve(result);
})
.catch((err) => reject(err));
});
promisesArray.push(promise);
}
Promise.all(promisesArray)
.then((result) => res.json(result))
.catch((err) => {
res.json(err);
});
});
app.listen(PORT, () => console.log(`server running on PORT ${PORT}`));

NodeJS: Why do I keep getting Cannot GET/

I am currently trying to make a webapp that uses the darksky api to pull weather data. I have the basic functionality done, but when I try to run it on port 3000, I get "Cannot GET/". I am quite new to using node and backend servers as a whole so I don't know how to debug this. I will paste my code below.
const express = require("express");
const unirest = require("unirest");
const credentials = require('./apiCredentials.json');
const app = express();
app.use(express.static('/public')); // location of my index.html
app.get('/weather', (req, res) => {
const {lat,lon} = req.query;
let request = unirest("GET",`https://${credentials.host}/${lat},${lon}`);
request.query({
lang:"en",
units:"auto"
});
request.headers({
"dark-sky.p.rapidapi.com": credentials.host,
"466375f66bmsh72031b571ea7c30p1f704fjsnc527236c3565": credentials.apiKey
});
request.end(response => {
if(response.error) res.status(500).end();
const{
summary,
precipProbability,
temperature,
windSpeed,
windBearing
} = response.body.currently;
res.status(200).send(
JSON.stringify({
summary: summary,
chanceOfRain: precipProbability,
temp: temperature,
wind:{
speed: windSpeed,
bearing: windBearing
}
})
);
});
});
app.listen(3000,()=>{
console.info('Listening on port :3000');
});

Bind problem in SQL query in Node, Express, Mysql2 app

I have been following a tutorial on setting up REST APIs in Node, using Express for an app that accesses an existing MariaDB database. My version only needs to read data and I have the DB co-located with the Node application (same host).
My goal for this entry-level example is to just access the data, using static SQL, so I can see it rendered in the web page by the JSON pritifier.
[Next, I want to present the data in a table (EJS?). Later, when I can get that to work, I'll add form controls (React?) to let a user specify start and end date bounds for the SQL query. Finally I'll aim to render the data as a line graph (D3js).]
The tutorial runs the web server successfully (it returns 'OK' on the base URL), but when I go to URL/solarData it tries an async function to getMultiple rows from the DB, it responds:
Bind parameters must not contain undefined. To pass SQL NULL specify JS null TypeError: Bind parameters must not contain undefined. To pass SQL NULL specify JS null
at /SunnyData/solarViz/node_modules/mysql2/lib/connection.js:628:17
at Array.forEach (<anonymous>)
at Connection.execute (/SunnyData/solarViz/node_modules/mysql2/lib/connection.js:620:22)
at /SunnyData/solarViz/node_modules/mysql2/promise.js:120:11
at new Promise (<anonymous>)
at PromiseConnection.execute (/SunnyData/solarViz/node_modules/mysql2/promise.js:117:12)
at Object.query (/SunnyData/solarViz/services/db.js:6:40)
at processTicksAndRejections (internal/process/task_queues.js:95:5)
at async Object.getMultiple (/SunnyData/solarViz/services/solarData.js:7:16)
at async /SunnyData/solarViz/routes/solarData.js:8:14
app.js:61
./app.js
const express = require('express');
const app = express();
const port = process.env.PORT || 3800;
const solarDataRouter = require('./routes/solarData');
app.use(express.json());
app.use(
express.urlencoded({
extended: true,
})
);
app.get('/', (req, res) => {
res.json({'message': 'ok'});
})
app.use('/solarData', solarDataRouter);
/* Error handler middleware */
app.use((err, req, res, next) => {
const statusCode = err.statusCode || 500;
console.error(err.message, err.stack);
res.status(statusCode).json({'message': err.message});
return;
});
app.listen(port, () => {
console.log(`Example app listening at http://localhost:${port}`)
});
./routes/solarData.js
const express = require('express');
const router = express.Router();
const solarData = require('../services/solarData');
/* GET solar data. */
router.get('/', async function(req, res, next) {
try {
res.json(await solarData.getMultiple(req.query.page));
} catch (err) {
console.error(`Error while getting solar data `, err.message);
next(err);
}
});
module.exports = router;
./config.js
const env = process.env;
const config = {
db: {
host: env.SUNNY_HOST,
user: env.SUNNY_USER,
password: env.SUNNY_PW,
database: env.SUNNY_DB,
},
listPerPage: env.LIST_PER_PAGE,
};
module.exports = config;
./services/solarData.js
const db = require('./db');
const helper = require('../helper');
const config = require('../config');
async function getMultiple(page = 1){
const offset = helper.getOffset(page, config.listPerPage);
const rows = await db.query(
`SELECT * FROM DTP LIMIT ?,?`, [offset, config.listPerPage]
);
const data = helper.emptyOrRows(rows);
const meta = {page};
return {
data,
meta
}
}
module.exports.getMultiple = getMultiple;
./services/db.js
const mysql = require('mysql2/promise');
const config = require('../config');
async function query(sql, params) {
const connection = await mysql.createConnection(config.db);
const [results, ] = await connection.execute(sql, params);
return results;
}
module.exports = {
query
}
I've left out the ./helper.js
Everything runs fine until I direct the webpage to /solarData. At that point I get the Debug Console (vscode) mentioned up-front
Searching seems to point at a mysql2 shortcoming/bug but not at a practical solution
If you respond, please describe the 'bind' mechanism, as I'm not sure what's going on.
Hope I've put enough info in. Please ask if I need to add anything else.

The error says
Bind parameters must not contain undefined.
It means that in the file ./services/solarData.js on the line
const rows = await db.query(
`SELECT * FROM DTP LIMIT ?,?`, [offset, config.listPerPage]
);
Some of the 2 variables is undefined, you need to check offset and config.listPerPage to be defined.
Just use
console.log('offset: ' + offset)
console.log('listPerPage: ' + config.listPerPage)
and you will find out what is undefined in your case

Express not rendering my React Front End?

I have two repos for the Front End and Back End portions of my project.
The Front End is a simple create-react-app project that hits my Express Back End and received responses from API calls.
I ran npm run build in my Front End project and moved that build folder to the root of my express backend repo.
However, when I try to reach the root page (i.e. localhost:3001), for some reason the response only returns the static html from index.html and doesn't actually render anything.
But if I go to something that has a path like localhost:3001/pokedex/1 then at least I see a correct response coming from the API.
I have a feeling that there is something wrong with the way I'm declaring my paths.
Here is the code on the Front End that is reaching out to the Back End:
import axios from 'axios'
const baseUrl = '/'
const getAll = () => {
const request = axios.get(baseUrl)
return request.then(response => response.data)
}
const getPkm = (id) => {
const request = axios.get(`${baseUrl}pokedex/${id}`)
return request.then(response => response.data)
}
export default { getAll, getPkm }
This is my Express Back End entry index.js:
const express = require('express')
const app = express()
const cors = require('cors')
const axios = require('axios')
//Middleware
app.use(cors())
app.use(express.json())
app.use(express.static('build'))
const unknownEndpoint = (request, response) => {
response.status(404).send({ error: 'unknown endpoint' })
}
let fullPkmList = require('./fullPkmList.json')
function ignoreFavicon(req, res, next) {
if (req.originalUrl.includes('favicon.ico')) {
res.status(204).end()
}
next();
}
app.get('/', (req, res) => {
axios.get(`https://pokeapi.co/api/v2/pokemon/?limit=100`)
.then((list) => res.json(list.data.results))
})
app.get('/pokedex/:id', (request, response) => {
const id = Number(request.params.id)
const pokemon = fullPkmList[id - 1]
if (pokemon) {
axios.all([
axios.get(`https://pokeapi.co/api/v2/pokemon/${id}`),
axios.get(`https://pokeapi.co/api/v2/pokemon-species/${id}`)
])
.then(axios.spread((pokemonResponse, speciesReponse) => {
let pkmResponse = pokemonResponse.data
let speciesResponse = speciesReponse.data
response.json({pkm: pkmResponse, species: speciesResponse })
}))
} else {
response.status(404).end()
}
})
app.use(unknownEndpoint)
const PORT = process.env.PORT || 3001
app.listen(PORT, () => {
console.log(`this is a test ${PORT}`)
})
Code for the Front End: https://github.com/rohithpalagiri/pocketdex
Code for the Back End: https://github.com/rohithpalagiri/pocketdex-backend
To see the issue, you only need to run the backend. I console log the response and in that, you will see the index.html file markup being returned. My goal is to have all of the paths relative so that the root url doesn't really matter. I think that is the part I'm getting stuck on.
I'd appreciate any help!

expressJS: How to push socketIO on get call?

This is how I set up a simple expressJS server with a socket.IO connection.
My application is reading some sensor data every 10 seconds, which gets pushed to every client. This is no problem for me.
But also one client can call /set-status with some parameter to change some status data. In that case the new status data should be send to every client. That's why a simple request/response attempt is not working.
What do I have to do to push the socketIO connection after /set-status has been called?
const express = require('express')
const http = require('http')
const socketIo = require('socket.io')
const app = express()
const server = http.createServer(app)
const io = socketIo(server)
io.on('connection', socket => {
getStatus(socket)
getData(socket)
setInterval(
() => getData(socket),
10000
)
})
app.get('/set-status', (req, res) => {
// Change some data and push new data to every client
// How to get access to socket?
res.send(200, 'new-data')
})
const getStatus = async socket => {
const res = { initial: 'data' }
socket.emit('exampleStatus', res)
}
const getData = async socket => {
// read some sensor data, which is refreshed every 10 sec.
// this is working as expected
const res = { some: 'sensor data' }
socket.emit('sensorData', res)
}
server.listen(port, () => {
if (process.env.NODE_ENV !== 'production') {
console.log(`Listening on port ${port}`)
}
})

If client sockets are listening for exampleStatus events, you can emit an exampleStatus event from inside of your get callback. It would look like this: io.emit('exampleStatus', data). On your client sockets, you can write a listener which looks like socket.on('exampleStatus, data => // do something with data).