retrieve parameters from Express using an intercepting middleware

Question

retrieve parameters from Express using an intercepting middleware

I am seeking a way to capture a req.params item in an interception layer:

Imagine having an instance of an express server application like this:

const app = express();

along with an interception layer:

app.use((req, res, next) => {
    console.log(req.params.myParam);
    next();
})

and multiple endpoints similar to this one:

app.get('/anything/:myParam', (req, res) => res.send('hello'))

Currently, 'undefined' is being logged, which is expected as the parameter name is not yet defined when the middleware within "use" is executed. However, I urgently need to access the value of myParam in this interception layer while adhering to the following constraints:

I know the specified name of the parameter in the intercepted endpoints (myParam)
I do not have knowledge of how the URL structure is set up in the intercepted endpoints (it could be /anything/:myParam, or /:myParam/anything, etc.)

Is there a solution available for this particular scenario?

javascript express

Answer 1

Answer №1

A helpful tip from @indrajaj26 on utilizing app.param() inspired me to find a solution that works.

Here is my approach:

/** Setting up an express application */
const app = express();

// Handling the interception
app.param('myParam', (req, res, next, myParam) => {
/* Storing myParam in a reusable manner (such as using locals as suggested by @nullromo).
 * In my case, I am employing zonejs: creating a forked zone with myParam stored in zone properties.
 */
    next();
});

// Accessing the intercepted data. Anywhere in the callstack of any endpoint utilizing "myParam" as a request parameter:
console.log(Zone.current.getZoneWith('myParam')?.get('myParam'));

Appreciate everyone for sharing their insights!

Answer 2

A helpful tip from @indrajaj26 on utilizing app.param() inspired me to find a solution that works.

Here is my approach:

/** Setting up an express application */
const app = express();

// Handling the interception
app.param('myParam', (req, res, next, myParam) => {
/* Storing myParam in a reusable manner (such as using locals as suggested by @nullromo).
 * In my case, I am employing zonejs: creating a forked zone with myParam stored in zone properties.
 */
    next();
});

// Accessing the intercepted data. Anywhere in the callstack of any endpoint utilizing "myParam" as a request parameter:
console.log(Zone.current.getZoneWith('myParam')?.get('myParam'));

Appreciate everyone for sharing their insights!

Answer 3

Answer №2

If you're looking for a straightforward solution, consider passing the middleware function at route definition.

For instance:

function myMiddleware(req, res, next) {
    console.log(req.params.myParam);
    next();
}

app.get('/path', myMiddleware, function(req, res) {
    ...
});

Here's a complete example:

const express = require('express');
const app = express();

function myMiddleware(req, res, next) {
    console.log(req.params.myParam);
    next();
}

app.get('/path', myMiddleware, function(req, res) {
    ...
});

app.listen(3000, () => console.log('server is up and running'));

Answer 4

If you're looking for a straightforward solution, consider passing the middleware function at route definition.

For instance:

function myMiddleware(req, res, next) {
    console.log(req.params.myParam);
    next();
}

app.get('/path', myMiddleware, function(req, res) {
    ...
});

Here's a complete example:

const express = require('express');
const app = express();

function myMiddleware(req, res, next) {
    console.log(req.params.myParam);
    next();
}

app.get('/path', myMiddleware, function(req, res) {
    ...
});

app.listen(3000, () => console.log('server is up and running'));

Answer 5

Answer №3

To utilize the params later on in middleware, you can save them to the response.locals object.

const express = require('express');

const app = express();

app.get('/:name', (request, response, next) => {
    // create a result based on the params
    const result = `Greetings, ${request.params.name ?? 'visitor'}!`;
    // store the params and result in response.locals
    response.locals = { params: request.params, result };
    // move on to the next middleware with the params and result
    next();
});

app.use((request, response, next) => {
    // access the stored params from the previous middleware
    console.log(`Captured: ${JSON.stringify(response.locals.params)}`);
    // finally send the desired response
    response.status(200).send(response.locals.result);
});

app.listen(3000, () => {
    console.log('Server is listening');
});

While this method involves saving request.params in every handler's response.locals, it eliminates the need for repeating an interceptor middleware if necessary.

Answer 6

To utilize the params later on in middleware, you can save them to the response.locals object.

const express = require('express');

const app = express();

app.get('/:name', (request, response, next) => {
    // create a result based on the params
    const result = `Greetings, ${request.params.name ?? 'visitor'}!`;
    // store the params and result in response.locals
    response.locals = { params: request.params, result };
    // move on to the next middleware with the params and result
    next();
});

app.use((request, response, next) => {
    // access the stored params from the previous middleware
    console.log(`Captured: ${JSON.stringify(response.locals.params)}`);
    // finally send the desired response
    response.status(200).send(response.locals.result);
});

app.listen(3000, () => {
    console.log('Server is listening');
});

While this method involves saving request.params in every handler's response.locals, it eliminates the need for repeating an interceptor middleware if necessary.

retrieve parameters from Express using an intercepting middleware

Answer №1

Answer №2

Answer №3

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