mongoose.connect部分给我带来了问题。如果我不包含useNewUrlParser：true，使用UnifiedTopology：true，在终端中运行app.js会给予我关于包含这些部分的DeprecationWarning。但是，如果我添加了它们，运行app.js什么也不做。它永远冻结了。

//jshint esversion:6

const mongoose = require("mongoose");

mongoose.connect("mongodb://localhost:27017/", {
    useNewUrlParser: true, useUnifiedTopology: true
});

//Schema is scaffolding of date. For instance here's one for fruits. 
const fruitSchema = new mongoose.Schema({
    name: String,
    rating: Number,
    review: String
});

//This part is also required for upper one to work. 
const Fruit = mongoose.model("Fruit", fruitSchema);

const fruit = new Fruit({
    name: "Apple",
    rating: 7,
    review: "I loved it."
});

fruit.save();