npm install -g

安装了全局的express 

G:\NodeJs\MyProject>node helloworld-Express.js

module.js:327

    throw err;

    ^

Error: Cannot find module ‘express‘

    at Function.Module._resolveFilename (module.js:325:15)

    at Function.Module._load (module.js:276:25)

    at Module.require (module.js:353:17)

    at require (internal/module.js:12:17)

    at Object.<anonymous> (G:\NodeJs\MyProject\helloworld-Express.js:1:76)

    at Module._compile (module.js:409:26)

    at Object.Module._extensions..js (module.js:416:10)

    at Module.load (module.js:343:32)

    at Function.Module._load (module.js:300:12)

    at Function.Module.runMain (module.js:441:10)

安装完Express之后执行文件报错