Express
Express.js is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications. This cheatsheet provides a quick reference to the most commonly used APIs, methods, and properties in Express.js. Use this guide to quickly look up syntax and options as you develop your Node.js applications.
Express.js API Reference
Comprehensive guide to Express.js APIs, including global objects and application properties.
/* *******************************************************************************************
* API
* http://expressjs.com/en/api.html
* ******************************************************************************************* */
`npm i express --save` or`yarn add -D express` `(-D saves it as a dev dependency)`
`yarn add -D @types/express` `(Installing for TS)`
const express = require("express"); // Importing the express library.
const app = express(); // Intializing the imported express application
/* *******************************************************************************************
* GLOBAL OBJECTS
* http://expressjs.com/en/api.html#express.json
* ******************************************************************************************* */
Methods
`express.json([options]);`
options: `
inflate // to manage the deflated bodies like enabling and disabling
limit // Controls the maximum request body size.
reviver // It is passed directly to JSON.parse as an second argument
type // This is used to determine the type of middleware will parse
verify // It is an undefined function which used to verify the middleware parsing.
`;
`express.raw([options]);`
options: `
inflate // to manage the deflated bodies like enabling and disabling
limit // Controls the maximum request body size.
type // This is used to determine the type of middleware will parse
verify // It is an undefined function which used to verify the middleware parsing.
`;
`express.Router([options]);`
options: `
caseSensitive //Enables case sensitivity
mergeParams //if param names of child and parent are conflicted then the child takes the precedence
strict // Enables Strict routing
`;
`express.static(root, [options]);`
options: `
dotfiles // determines how dotfiles are used
etag // Operates etag generation
extensions // Operates file extension fallback
fallthrough // Enable or disable the immutable directive in the Cache-Control response header
index // sends the specified directory index file
LastModified // sets the Last-Modified header to the last modified date
setHeaders // Function for setting HTTP headers to serve with the file
`;
`express.text([options]);`
options: `
defaultCharset // Sets the default charset for the text context.
inflate // to manage the deflated bodies like enabling and disabling
limit // Controls the maximum request body size.
type // This is used to determine the type of middleware will parse
verify // It is an undefined function which used to verify the middleware parsing.
`;
`express.urlencoded([options]);`
options: `
extended // it allows to choose between parsing the URL-encoded data or the qs library
parameterLimit // It controls the no of params.
inflate // to manage the deflated bodies like enabling and disabling
limit // Controls the maximum request body size.
type // This is used to determine the type of middleware will parse
verify // It is an undefined function which used to verify the middleware parsing.
`;
Application
Details on Express application settings and properties.
Properties
`app.local`;
`app.locals.title = "My Cheatsheet";
console.dir(app.locals.title)`; `// Creating objects with local variables`
app.mountpath`
``app.mountpath``const admin = express()
admin.get('/', function(req,res){
console.log(admin.mountpath)
res.send('Admin Homepage')
})
app.use('<admin dir>', admin)`; `// Mounting a sub - app`
``Event``
`admin.on('mount', (parent){
console.log('Admin Mounted')
})` `// Mounting on a parent app`
Methods
`app.get('/', function(req, res){
res.send('GET request to message')
})` `// get requests to the specified path`
`app.post('/', function(req,res){
res.send('POST request to a webpage')
})` `// post request to the specified path`
`app.put('/', function(req,res){
res.send('PUT request to a webpage')
})` `// post request to the specified path`
`app.delete('/', function(req,res){
res.send('DELETE request to a webpage')
})` `// delete request to the specified path`
`app.all('/', function(req,res,next){
console.log('Accessing the secret section....')
next()
})` `// Routing all types of HTTP request`
`app.param('user', function(req,res,next){
User.find(id, function(err, user){
if(err){
next(err)
} else if (user){
req.user = user
next()
} else {
next(new Error('Failed to load user'))
}
})
})` `// Adding callback trigger to route parameters`
`app.use(function(req,res,next){
res.send('Hey There!')
})` `// To Invoke the middleware layer that you want to add`
Request
Details on Express request properties and methods.
Methods
`req.get('content-type')` `// Returns the specified HTTP req header`
`req.accepts('html')` `// Checks if the specified content types are available or not`
`req.is('json')` `// Requests the matching content-type`
`var range = req.range(1000)
if (range.type === 'bytes'){
range.forEach(function(r){
// Your code
})
}` `// Range header parser`
Properties
`req.param('name')` `// Requests the param name when present`
`app.post('/', function (req, res, next) {
console.log(req.body)
res.json(req.body)
})` `// Data submitted in the request body`
`console.dir(req.cookies.name)` `// Contains cookies sent by the request`
`console.dir(req.query.q)` `// Query string parameter in the route`
`console.log(req.route)
res.send('GET')` `// Outputs all the layer, methods, path`
`console.dir(req.signedCookies.user)` `// Logs all the signed cookies sent by the request`
Response
Details on Express response methods.
Methods
`res.redirect('https://google.com')` `// Redirects to the intended page`
`res.send({message: 'Awesome Stuffs'})` `// Response to the webpage`
`res.json({alert: 'awesomecheatsheets'})` `// Response in JSON type`
`const file = req.params.name;
res.sendFile(file, options, function(err){
if(err){
next(err)
}else{
console.log('Sent:', file)
}
})` `// Sends file to the intended path`
`res.render('index')` `// Rendering the intended file`
BodyParser
Details on using BodyParser middleware.
`const BodyParser = require('body-parser')
app.use(BodyParser.json())
app.use(BodyParser.urlencoded({
extended: true
}))` `// Parses incoming request bodies`For more information, refer to the official Express.js documentation and the BodyParser documentation.