使用脚手架生成器
//在全局安装脚手架
npm install express-generator -g 
npm install express --save  安装express

或者 

 emall-backend --view=ejs   指定视图模式为ejs
express emall-backend  创建一个项目文件夹
 日志输出
  warning: the default view engine will not be jade in future releases
  warning: use `--view=jade' or `--help' for additional options

   create : emall-backend\
   create : emall-backend\public\
   create : emall-backend\public\javascripts\
   create : emall-backend\public\images\
   create : emall-backend\public\stylesheets\
   create : emall-backend\public\stylesheets\style.css
   create : emall-backend\routes\
   create : emall-backend\routes\index.js
   create : emall-backend\routes\users.js
   create : emall-backend\views\
   create : emall-backend\views\error.jade
   create : emall-backend\views\index.jade
   create : emall-backend\views\layout.jade
   create : emall-backend\app.js
   create : emall-backend\package.json
   create : emall-backend\bin\
   create : emall-backend\bin\www

   change directory:
     > cd emall-backend    进入项目目录

   install dependencies:
     > npm install   安装

   run the app:
     > SET DEBUG=emall-backend:* & npm start   启动
 在浏览器输入 http://localhost:3000 
 显示
   Express
Welcome to Express    说明环境搭建成功

vscode 执行命令 npm strat 报错

npm start + ~~~ + CategoryInfo : SecurityError: (:) []，PSSecurityException + FullyQualifiedErrorId : UnauthorizedAccess

解决办法

临时

Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope Process -Force

永久

# 以管理员身份运行 PowerShell
Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Force