Stack Overflow Asked on December 27, 2021
I am trying to learn Web APIs. I was writing a simple code that gets data from the server in the log after clicking a button, but I keep getting an error in the server side, which is "Cannot set headers after they are sent to the client".
My server side code:
const express = require("express");
const cors = require("cors");
const bodyParser = require("body-parser");
const app = express();
projectData = [];
app.use(bodyParser.urlencoded({extended: false}));
app.use(bodyParser.json());
app.use(cors());
app.use(express.static("website"));
const port = 9013;
const server = app.listen(port, listening);
function listening () {
console.log("running localhost"+port);
}
let someData = {name:"name", num:"num"};
app.get ('/hello', function (req, res){
res.send("Get request response");
res.send(someData);
})my client side code is:
const generate = document.getElementById("generate");
generate.addEventListener("click", performAction);
function performAction (e) {
getDemo();
}
const getDemo = async () => {
const res = await fetch ("/hello");
try {
const data = await res.json();
console.log(data);
}
catch (error) {
console.log("erroor");
}
}Thanks for helping.
That problem is something very basic. Here:
app.get ('/hello', function (req, res){
res.send("Get request response");
res.send(someData);
})
You cannot send a second response back. You already sent Get request response back to the client.
1 request = 1 response from server. Thats all. Remove 1 line:
app.get ('/hello', function (req, res){
res.send(someData);
})
Bonus: Just a hint, you should put your fetch inside the try / catch block not outside.
Answered by Ifaruki on December 27, 2021
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