Between express server and react.js - fetch does not work? - ajax

Question

I am trying to get data in react by sending GET or POST request to express server.
But I can't receive response from server.
Below is my React component code.
handleButton() {
const sendData = {
"say" : "Hello",
"to" : "React App"
};
fetch("http://localhost:5000/", {
mode : "no-cors",
method : "POST",
body : JSON.stringify(sendData)
}).then(res => {
console.log(res);
alert(res);
});
}
handleButton() is called when I press the button.
I want to receive data from server when I click the button.
Then here is my express server code.
var express = require("express");
var bodyParser = require("body-parser");
var multer = require("multer");
var upload = multer();
var app = express();
app.get("/", function(req, res) {
res.render("form");
});
app.set("view engine", "pug");
app.set("views", "./views");
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({extended : true}));
app.use(upload.array());
app.use(express.static("public"));
app.post("/", function(req, res) {
console.log(req.body);
res.send("received your request!");
});
app.listen(5000);
My server is very simple but it doesn't work.
When I press the button, server console outputs empty object.
This is my server console capture image.
And then this is my google chrome browser console capture image.
Please help me with getting right result. I want to notice that server received request by alert in react.