In this tutorial, we are going to be talking about Express Framework in Node.js.<\/p>\n
You will learn what the Express framework is. You’ll also learn how to set up and use Express Framework.<\/p>\n
<\/p>\n
The Express Framework also called express.js is a web application server framework that works with Node.js. You can used it to quickly build web applications like single-page applications and mobile applications.<\/p>\n
Features of the express framework include:<\/p>\n
<\/p>\n
To set up express simply run the command<\/p>\n
npm install express\r\n<\/pre>\nAfter running this command, a folder is created in your application folder containing all the downloaded modules.<\/p>\n
You’ll also need to install the following additional modules:<\/p>\n
<\/p>\n
Let’s write a simple express app that creates and starts a web server listening at port 8080. When a request comes from a client, the app responds with a message ‘Welcome to Express Framework’.<\/p>\n
<\/p>\n
\/\/Demo Express App by Kindson The Genius<\/span>\r\nvar<\/span> express =<\/span> require('express'<\/span>);\r\nvar<\/span> app =<\/span> express();\r\n\r\napp.get('\/'<\/span>, function<\/span>(req, res){\r\n res.send('Welcome to Express'<\/span>);\r\n})\r\n\r\nvar<\/span> server =<\/span> app.listen(8080<\/span>, function<\/span>(){\r\n var<\/span> host =<\/span> server.address().address\r\n var<\/span> port =<\/span> server.address().port\r\n\r\n console.log(\"Demo web app listening at http:\/\/%s:%s\"<\/span>, host, port)\r\n})\r\n<\/pre>\n <\/p>\n
Run the code above. The visit http:\/\/localhost:8080, then you can see the page displays with the message ‘Welcome to Express’.<\/p>\n
<\/p>\n
4. Request and Response in Express<\/strong><\/h5>\nAn application create with express makes use of callback function. The function would take two parameters: request and response. This is as shown below<\/p>\n
<\/p>\n
<\/p>\n
app.get('\/'<\/span>, function<\/span>(req, res){\r\n res.send('Welcome to Express'<\/span>);\r\n})\r\n<\/pre>\n <\/p>\n
\n- A request object represents a http request coming from a client. It has all the properties of a request including url query string, request body, http header\u00a0 and body<\/li>\n
- A response object represents\u00a0 a http response provided by the server<\/li>\n<\/ul>\n
You can also obtain the properties of the request and response objects to examine them or print them out to the console<\/p>\n
<\/p>\n
5. Routing Using Express<\/strong><\/h5>\nNow we would talk about something very important: routing.<\/p>\n
How do control the endpoint that is reached based on the url path provided?\u00a0 Also routing helps us route a request based on the http method. For instance a POST request, GET request, PUT or DELETE request.<\/p>\n
Let’s work with our previous demo webapp. This time, we’ll extend it to include routing feature. This is as easy as just changing app.get() to app.post() and a little more. Let’s do it<\/p>\n
<\/p>\n
\/\/Demo Express App by Kindson The Genius<\/span>\r\nvar<\/span> express =<\/span> require('express'<\/span>);\r\nvar<\/span> app =<\/span> express();\r\n\r\n\/\/ Handles a \"GET Request for home\" on the homepage<\/span>\r\napp.get('\/'<\/span>, function<\/span> (req, res) {\r\n console.log(\"GET request for the homepage\"<\/span>);\r\n res.send('Welcome to GET!'<\/span>);\r\n})\r\n\r\n\/\/ Handles a POST request for the homepage<\/span>\r\napp.post('\/'<\/span>, function<\/span> (req, res) {\r\n console.log(\"POST request for the homepage\"<\/span>);\r\n res.send('Welcome to POST!'<\/span>);\r\n})\r\n\r\n\/\/ Handles a DELETE request for the \/del_user page.<\/span>\r\napp.delete<\/span>('\/del_user'<\/span>, function<\/span> (req, res) {\r\n console.log(\"DELETE request coming from \/del_user\"<\/span>);\r\n res.send('Welcome to DELETE!'<\/span>);\r\n})\r\n\r\n\/\/ Handles a GET request for the \/list_user page.<\/span>\r\napp.get('\/list_user'<\/span>, function<\/span> (req, res) {\r\n console.log(\"GET Request comming from \/list_user\"<\/span>);\r\n res.send('List of User'<\/span>);\r\n})\r\n\r\n\/\/ Handles a get request whose part correspond to the url pattern<\/span>\r\n\/\/wxyz, wxayz, wxmyyz etc<\/span>\r\napp.get('\/wx*yz'<\/span>, function<\/span>(req, res) { \r\n console.log(\"GET Request comming from \/wx*yz\"<\/span>);\r\n res.send('URL Pattern Match'<\/span>);\r\n})\r\n\r\nvar<\/span> server =<\/span> app.listen(8080<\/span>, function<\/span> () {\r\n var<\/span> host =<\/span> server.address().address\r\n var<\/span> port =<\/span> server.address().port\r\n \r\n console.log(\"Demo app listening at http:\/\/%s:%s\"<\/span>, host, port)\r\n})\r\n<\/pre>\nSave the code and then run it.<\/p>\n
Try to visit these urls and observe the output<\/p>\n
\n- http:\/\/localhost\/8080<\/li>\n
- http:\/\/localhost\/list_user<\/li>\n<\/ul>\n
In the next part, I will teach you how to use Advanced REST Client to make DELETE and POST requests<\/p>\n","protected":false},"excerpt":{"rendered":"
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