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Node.js/Libs/express.md

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+# [Express](https://expressjs.com/)
+
+## Installation
+
+```ps1
+npm install express --save
+```
+
+## [Application](https://expressjs.com/en/4x/api.html#app)
+
+```js
+const express = require("express");
+
+const app = express();
+const PORT = 5555;
+
+// correctly serve static contents
+app.use(express.static("/route/for/static/files", "path/to/static/files/folder"));
+
+// HTTP GET
+app.get("/<route>:<param>", (req, res) => {
+    console.log(`${req.connection.remoteAddress} requested ${req.url}`);
+});
+
+// HTTP POST
+app.post("/<route>:<param>", (req, res) => {
+    console.log(`${req.connection.remoteAddress} posted to ${req.url}`);
+});
+
+// responds to all HTTP verbs
+app.all("/<route>:<param>", (req, res, next) => { 
+    next();  // handle successive matching request (valid also on .get() & .post())
+});
+
+let server = app.listen(PORT, () => {
+    console.log(`Express server listening at http://localhost:${PORT}`);
+});
+
+server.on("error", () => {
+    server.close();
+});
+```
+
+## [Response](https://expressjs.com/en/4x/api.html#res)
+
+```js
+Response.send([body]);  // Sends the HTTP response.
+Response.sendFile(path);  // Transfers the file at the given path.
+Response.json(body);  // Sends a JSON response.
+Response.redirect([status,] path);  // Redirects to the URL derived from the specified path, with specified status
+Response.end();  // Ends the response process
+```
+
+## [Request](https://expressjs.com/en/4x/api.html#req)
+
+```js
+Request.params.<param>  // query params obj (GET)
+Request.body.<param>  // body params (POST)
+```