[mabel] Add versioning for library with routers

Author: mabelleeyanhwa

library.js

@@ -0,0 +1,12 @@
+const express = require("express");
+const apiVersion1 = require("./library_v1");
+const apiVersion2 = require("./library_v2");
+const app = express();
+const PORT = 3000;
+
+app.use("/v1", apiVersion1);
+app.use("/v2", apiVersion2);
+
+const server = app.listen(PORT, () => {
+  console.log(`Library API running on http://localhost:${PORT}`);
+});

library_v1.js

@@ -0,0 +1,15 @@
+const express = require("express");
+const api = express.Router();
+const PORT = 3000;
+
+const booksRouter = require("./routes/books");
+const usersRouter = require("./routes/users");
+
+api.use("/books", booksRouter);
+api.use("/users", usersRouter);
+
+api.get("/", (req, res) => {
+  res.send("Version 1 of library API");
+});
+
+module.exports = api;

library_v2.js

@@ -0,0 +1,15 @@
+const express = require("express");
+const api = express.Router();
+const PORT = 3000;
+
+const booksRouter = require("./routes/books");
+const usersRouter = require("./routes/users");
+
+api.use("/books", booksRouter);
+api.use("/users", usersRouter);
+
+api.get("/", (req, res) => {
+  res.send("Version 2 of library API");
+});
+
+module.exports = api;