Request parameters
I mentioned how the Request object holds all the HTTP request information.
These are the main properties you’ll likely use:
| Property | Description |
|---|---|
| .app | holds a reference to the Express app object |
| .baseUrl | the base path on which the app responds |
| .body | contains the data submitted in the request body (must be parsed and populated manually before you can access it) |
| .cookies | contains the cookies sent by the request (needs the cookie-parser middleware) |
| .hostname | the hostname as defined in the Host HTTP header value |
| .ip | the client IP |
| .method | the HTTP method used |
| .params | the route named parameters |
| .path | the URL path |
| .protocol | the request protocol |
| .query | an object containing all the query strings used in the request |
| .secure | true if the request is secure (uses HTTPS) |
| .signedCookies | contains the signed cookies sent by the request (needs the cookie-parser middleware) |
| .xhr | true if the request is an XMLHttpRequest |
How to retrieve the GET query string parameters using Express
The query string is the part that comes after the URL path, and starts with a question mark ?.
Example:
?name=flavio
Multiple query parameters can be added using &:
?name=flavio&age=35
How do you get those query string values in Express?
Express makes it very easy by populating the Request.query object for us:
const express = require('express')
const app = express()
app.get('/', (req, res) => {
console.log(req.query)
})
app.listen(8080)
This object is filled with a property for each query parameter.
If there are no query params, it’s an empty object.
This makes it easy to iterate on it using the for…in loop:
for (const key in req.query) {
console.log(key, req.query[key])
}
This will print the query property key and the value.
You can access single properties as well:
req.query.name //flavio
req.query.age //35
How to retrieve the POST query string parameters using Express
POST query parameters are sent by HTTP clients for example by forms, or when performing a POST request sending data.
How can you access this data?
If the data was sent as JSON, using Content-Type: application/json, you will use the express.json() middleware:
const express = require('express')
const app = express()
app.use(express.json())
If the data was sent using Content-Type: application/x-www-form-urlencoded, you will need to use the express.urlencoded() middleware:
const express = require('express')
const app = express()
app.use(express.urlencoded({
extended: true
}))
In both cases you can access the data by referencing it from Request.body:
app.post('/form', (req, res) => {
const name = req.body.name
})
Note: older Express versions required the use of the
body-parsermodule to process POST data. This is no longer the case as of Express 4.16 (released in September 2017) and later versions.
Download my freeNode.js Handbook!
Download my free Programming Ebooks!