node.js报错：Cannot find module 'ejs'的解决办法

Error: Cannot find module 'ejs'
  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 new View (d:\WebClient\webstormSpace\day6shuoshuo\node_modules\express\lib\view.js:78:30)
  at EventEmitter.render (d:\WebClient\webstormSpace\day6shuoshuo\node_modules\express\lib\application.js:569:12)
  at ServerResponse.render (d:\WebClient\webstormSpace\day6shuoshuo\node_modules\express\lib\response.js:961:7)
  at exports.showIndex (d:\WebClient\webstormSpace\day6shuoshuo\routes\router.js:7:9)
  at Layer.handle [as handle_request] (d:\WebClient\webstormSpace\day6shuoshuo\node_modules\express\lib\router\layer.js:95:5)
  at next (d:\WebClient\webstormSpace\day6shuoshuo\node_modules\express\lib\router\route.js:131:13)