How should I parse URL parameters using Node JS express?

Question

I would like to pass the lat lon from this URL http://localhost:8080/fp?lon=103.742463567216646&lat=1.336711421273283. Where should I place the "req.query.lon" and "req.query.lat" in the following code?

I am hoping to parse the users input in the URL link so that I can dynamically retrieve from the database.

const {Client} = require("pg")
const express = require ("express")
const url=require('url')
const fs= require('')
const app = express();
app.use(express.json())

const client = new Client({
    "user": "xxx",
    "password" : "xxx",
    "host" : "xxx",
    "port" : xxx,
    "database" : "xxx"
})

//app.get("/", (req, res) => res.sendFile(`${__dirname}/index.html`))

app.get("/fp", async (req, res) => {
    //const lon = 103.742463567216646;
    //const lat = 1.336711421273283;
    //const lon = req.query.lon;
    //const lat = req.query.lat;
    const rows = await readTodos ();

    res.send(JSON.stringify(rows))
})





app.listen(8080, () => console.log("Web server is listening.. on port 8080"))

start()

async function start() {
    await connect();


}


async function connect() {
    try {
        await client.connect();
    }
    catch(e) {
        console.error(`Failed to connect ${e}`)
    }
}

async function readTodos() {
    try {
    const results = await client.query("SELECT ST_AsText(ST_Force2D(geom)) FROM fp ORDER BY geom <-> ST_SetSRID(ST_MakePoint("+lon+ ","+lat+ "), 3993) LIMIT 1;");
    return results.rows;
    }
    catch(e){
        return [];
    }
}

The place you have commented is the correct code. You can have them there, pls uncomment them and it works — Gvs Akhil
– Gvs Akhil, Commented May 4, 2020 at 2:46
I don't understand what you're asking for help with. If you are properly passing the URL as shown in your question, then the req.query.lon and req.query.lat are the right way to access query parameters on that URL. — jfriend00
– jfriend00, Commented May 4, 2020 at 2:58

Naor Levi · Accepted Answer · 2020-05-04 07:06:21Z

0

Express parses it by default and store them in req.query. Accessing req.query.<key> will give you the value you are looking for. For instance, in your example, express will store it inside req.query.lon and req.query.lat. So, actually you access them right in the request handler of /fp, just comment out the access to these variables and pass them as parameters to readTodos():

app.get("/fp", async (req, res) => {
    const lon = req.query.lon;
    const lat = req.query.lat;
    const rows = await readTodos(lon, lat);

    res.send(JSON.stringify(rows))
})

async function readTodos(lon, lat) {
    try {
    const results = await client.query("SELECT ST_AsText(ST_Force2D(geom)) FROM fp ORDER BY geom <-> ST_SetSRID(ST_MakePoint("+lon+ ","+lat+ "), 3993) LIMIT 1;");
    return results.rows;
    }
    catch(e){
        return [];
    }
}

answered May 4, 2020 at 7:06

Naor Levi

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