English
[Node.js] Use express
Sun Mar 21 2021
nodejs
express
route
1. Introdution
If you use node.js as a server, let's learn about express.js, which is considered the most standard. node.js is very easy to develop RESTful APIs.
2. Configuration Settings
Prerequisite Actions
Naturally, node.js is assumed to be installed.
If you haven't installed it, click here to install it.
First, let's create a folder to create a node.js development environment.
## Creating and opening folders
mkdir express_practice
cd express_practice
## init package.json
npm init -y
## install http, express modules
npm install http express3. Print Hello world!
Let's write a code to print Hello world.
// helloworld.js file
const express = require("express");
const http = require("http");
const app = express();
const server = http.createServer(app);
const PORT = 8080;
app.get("/", (req, res) => {
res.send("Hello world");
});
server.listen(PORT, () => {
console.log(`Server running on http://localhost:${PORT}`);
});After running, try connecting to http://localhost:8080 through a browser or postman.
node helloworld.js4. RESTful API
Let's implement a simple RESTful API to CRUD the user's account information.
// rest.js file
const express = require("express");
const http = require("http");
const bodyParser = require("body-parser");
const app = express();
app.use(bodyParser.urlencoded({ extended: false }));
const server = http.createServer(app);
const PORT = 8080;
// Temporary user id, password
let users = [
{
id: "hello",
password: "1234",
},
{
id: "world",
password: "1234",
},
];
// Return index of user in temporary user array
const findUserIndex = id => {
let index = -1;
let len = users.length;
for (let i = 0; i < len; i++) {
if (users[i].id === id) {
index = i;
break;
}
}
return index;
};
// Register a new user with a temporary user array
const register = (id, password) => {
let index = findUserIndex(id);
if (index !== -1) return false;
users.push({ id, password });
return true;
};
// Check if id, password exists in temporary user array
const login = (id, password) => {
let index = findUserIndex(id);
if (index === -1) return false;
if (users[index].id === id && users[index].password === password)
return true;
return false;
};
// Change the password in the temporary user array
const changePassword = (id, password) => {
let index = findUserIndex(id);
if (index === -1) return false;
users[index].password = password;
return true;
};
// Delete user from temporary user array
const deleteUser = id => {
let index = findUserIndex(id);
if (index === -1) return false;
users.splice(index, 1);
return true;
};
// register api
app.post("/", (req, res) => {
let id = req.body.id;
let password = req.body.password;
if (!register(id, password)) return res.status(401).send("duplicate id");
res.send(`success to register ${id}'s account`);
});
// Get information for a specific user
app.get("/:id", (req, res) => {
let id = req.params.id;
if (findUserIndex(id) === -1) return res.status(401).send("invalid id");
res.send(`Hello world ${id}`);
});
// Modifying specific user information
app.put("/:id", (req, res) => {
let id = req.params.id;
let password = req.body.password;
if (!changePassword(id, password))
return res.status(401).send("password change fail");
res.send(`success to change ${id}'s password`);
});
// Delete a specific user
app.delete("/:id", (req, res) => {
let id = req.params.id;
if (!deleteUser(id)) return res.status(401).send("delete fail");
res.send(`success to delete ${id}'s account`);
});
// user login
app.post("/login", (req, res) => {
let id = req.body.id;
let password = req.body.password;
if (!login(id, password)) return res.status(401).send("login fail");
res.send("hello " + id);
});
server.listen(PORT, () => {
console.log(`Server running on http://localhost:${PORT}`);
});