You have 3 files to build. Package.json was created by npm -init
Enter the code into your Node Application Development environment:
server.js
// 0. import a built-in library called "path"
const path = require("path")
// 1. import express into the Javascript program
const express = require("express")
// 2. Initialize express
const app = express()
// 3. Specify the port that you want your webserver to run on
// - by default, it will run on port 3000
const port = process.env.PORT || 3000
// -------
// In this section, define the server's behaviour
// - defining the endpoints that the server will respond to
// when the person comes to the main page (localhost:xxxx/), then do something
app.get("/", (req, res) => {
res.send("HELLO WORLD!")
})
// define the about endpoint
app.get("/about", (req, res) => {
// by default, res.send() is used to send string data back to a client
res.send("Welcome to the About endpoint")
})
// define the about endpoint
app.get("/faq", (req, res) => {
// the endpoint can send string containing HTML back to the client
// if the client is a browser, it will render this string as HTML
res.send("<h1>FAQ Page</h1><ol><li>How do servers work?</li><li>What is node?</li></ul>")
})
app.get("/contact", (req, res) => {
// res.send() can also be used to send files back to the client
// in this example, we send the HTML file located in the server's view/s directory
res.sendFile(path.join(__dirname, "/views/contact-us.html"))
})
// endpoints can be any length and any complexity
// - server performs "pattern matching to determine which endpoint should
// respond to the request
app.get("/students", (req, res) => {
res.send("Students!")
})
app.get("/students/gbc", (req, res) => {
res.send("GBC Students!")
})
app.get("/students/mycollege", (req, res) => {
res.send("mycollege Students!")
})
app.get("/students/mycollege/accounting", (req, res) => {
res.send("mycollege accounting Students!")
})
// in real life, some endpoints may be used transmit additional information to the server
// - for example, in many e-commerce websites, the endpoints
// contain information about the product's id or sku
// - if you have only a few products, you "could" manually code
// the product ids into each endpoint. But, this is tedious and difficult to maintain
// app.get("/products/6018-408", (req, res) => {
// res.send("Show Yellow shirt!")
// })
// instead, developers create endpoints with contain url parameters
// - url parameters communicate information to the server
app.get("/products/:category/:productId", (req, res) => {
// use req.params to access the value of :category and :productId
console.log(req.params)
// req.params is a Javascript object
console.log(`What is the data type of req.params? ${typeof(req.params)}`)
console.log(`What is the category: ${req.params.category}`)
console.log(`What is the productId: ${req.params.productId}`)
// choose what should be displayed based on the category
if (req.params.category === "kids-clothing") {
res.send("There are 5 products in the kids clothing category")
}
else if (req.params.category === "sunglasses") {
res.send("There are 100 sunglasses")
}
else {
res.send(req.params)
}
})
// exercise:
// write an endpoint that accepts a number and a math operation
// if the math operation is +, then the endpoint will display
// the sum of all values from 1 to the number
// if the math operation is *, then the endpoint will display
// the product of all values from 1 to the number
// if the operation is something else, then output -1
// the maximum number that can be selected is 10
// 1. get the number & convert it to a number before you can do math on it
const numFromUrl = parseInt(req.params.num)
// - check that person provided a number
if (isNaN(numFromUrl) === true) {
res.send(`Error: you must enter a number, ${req.params.num} is not a number`)
return
}
// - check for maximum value on the nubmer
if (numFromUrl > 10) {
res.send(`Error: max value is 10, ${req.params.num} is greater than 10`)
return
}
// 2. get the operation and do the math based on the operation
if (req.params.operation === "plus") {
// sum
let sum = 0
for (let i = 0; i < numFromUrl; i++) {
sum = sum + i
}
res.send(`The result of adding is ${sum}`)
}
else if (req.params.operation === "multiply") {
let result = 1
for (let i = 1; i <= numFromUrl; i++) {
result = result * i
}
res.send(`The result of multiply is ${result}`)
}
else {
// output -1
res.send("-1")
}
})
// catch-all router --> is an endpoint that is executed when
// the user types in an endpoint that doesn't exist
app.use((req,res) => {
// res.status(404).send("404 This page does not exist")
res.status(404).sendFile(path.join(__dirname, "/views/404.html"))
})
// --------
// - this function will execute when the server is started
const startServer = () => {
console.log(`The server is running on http://localhost:${port}`)
console.log(`Press CTRL + C to exit`)
}
// 4. Start the server on the specified port
// 5. What should happen when the server runs
app.listen(port, startServer)
