expressjsHow do I set and use headers in Express.js?

To set and use headers in Express.js, you can use the app.use() and res.header() methods.

The app.use() method is used to set the headers for all requests and responses. For example, the following code sets the Content-Type header to application/json for all requests and responses:

app.use(function (req, res, next) {
    res.header("Content-Type", "application/json");
    next();
});

The res.header() method is used to set the headers for a specific request and response. For example, the following code sets the Content-Type header to application/json for a specific response:

app.get("/", function (req, res) {
    res.header("Content-Type", "application/json");
    res.send({"message": "Hello World!"});
});

Output example

{"message": "Hello World!"}

The req.header() method is used to get the headers for a specific request. For example, the following code gets the Content-Type header for a specific request:

app.get("/", function (req, res) {
    let contentType = req.header("Content-Type");
    console.log(contentType);
});

Output example

application/json

Helpful links

• Express.js Documentation
• MDN Web Docs - HTTP Headers

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