app.js

var express = require("express");
var app = express();
var sounds = {'cow':'moe ',
            'cat':'meow ',
            'dog':'woof ',
            'bird':'tweet ',
            'mouse':'beep'};

app.get("/:animal/:count",function(req,res) {
    var animal = req.params.animal;
    var count = parseInt(req.params.count);
    var sound = sounds[animal];

    res.send("The " + animal + " says " + sound.repeat(count) + "!");
});

app.get("*",function(req,res) {
    res.send("Sorry, page not found. Please enter /animal/count ...");
});

app.listen(process.env.PORT, process.env.IP,function(){
    console.log("Server is running ...");
});

package.json

{
  "name": "34_js_node_get",
  "version": "1.0.0",
  "description": "Node express Demo",
  "main": "app.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "express": "^4.16.4"
  }
}