如何从 XMLHttpRequest 传入参数？

Question

I'm making an experiment with express and XHR . And I came up with a problem that after passing a params in xhr.send(params) didn't recieve it on the app.post() . I don't know if my code is correct but here it is.

My app.js file:

app.post('/', urlencodedParser, async (req, res) => {
    console.log('Received a request!', req.body); // I also tried req.params, req.query and still the same
    // output: "Recieved a request! {}"
    res.end('respond!');
});

Here's my script.js file:

xhr.open('POST', '/', true);
        xhr.setRequestHeader('Content-Type', 'application/json');
        xhr.setRequestHeader('Accept', 'application/json');
        xhr.send(JSON.stringify({
            name: 'SomeName'
        }));

Why is it that the params is empty when I recivied it in the app.js ? Is this how you really pass in parameters?

Answer 1

You need this:

app.use(express.json())

somewhere before your app.post() handler. That middleware will read the body of the response and parse the JSON and put the resulting Javascript properties into the req.body object for your later request handler to examine.

If you don't have that middleware, then the body of the POST is never read and thus req.body is never populated.