DeprecationWarning: collection.ensureIndex is deprecated. Use createIndexes instead

// 引入mongoose模块

const mongoose = require('mongoose');

// 链接数据库

mongoose.set('useCreateIndex', true) //加上这个

mongoose.connect('mongodb://localhost/xxxxxxxxx',{useNewUrlParser: true,useUnifiedTopology: true})

        .then(()=>console.log('数据库连接成功'))

        .catch(()=>console.log('数据库连接失败'))