Require is not defined when it is.

'use strict';

var mongoose = require("mongoose");

mongoose.connect("mongodb://localhost:27017/sandbox");

var db = mongoose.connection;

db.on("error", function(err){
    console.error("connection error:", err);
});

db.once("open", function(){
    console.log("Db connection success");
    //All db communication goes here

    var Schema = mongooose.Schema;
    var AnimalSchema = new Schema({
        type: String,
        color: String,
        size: String,
        mass: Number,
        name: String
    });

    var Animal = mongoose.model("Animal", AnimalSchema);

    var elephant = new Animal({
        type: "elephant",
        color: "gray",
        size: "big",
        mass: 6000,
        name: "Lawrence"
    });

    elephant.save(function(err) {
        if(err) console.error("save failed.", err);
        else console.log("saved!");
        db.close(function(){
            console.log("db connection closed");
        });
    });

});