我正在学习使用MongoDB和mongoose.js。我想插入一个文档并更新它。当我运行app.js时，它会记录“已成功更新”，但当我在mongo shell中预览它时，没有任何修改，即：“美丽的红色”保持不变。

const mongoose = require('mongoose');

// Connection URL
const url = 'mongodb://localhost:27017/fruitsDB'; //creates fruitsDB

// Connect to database server
mongoose.connect(url, {
  useNewUrlParser: true,
  useUnifiedTopology: true
});

// Define a schema/table structure
const fruitSchema = new mongoose.Schema({
  name: {
    type: String,
    required: [true, "No name specified. Try Again!"] //validation with error message
  },
  rating: {
    type: Number,
    min: 1, //validation
    max: 10 //validation
  },
  review: String
});

// Create a model from the structure
const Fruit = mongoose.model("Fruit", fruitSchema);

// Create a document that follows a model
const fruit = new Fruit({
  name: "Apple",
  rating: 6,
  review: "Pretty Red."
});

// Save the new document/entry
fruit.save();

// Update single document
Fruit.updateOne({name: "Apple"}, {review: "Review Changed!"}, function(err) {
  if(err) {
    console.log(err);
  } else {
    console.log("Successfully updated.");
  }
});