could you tell me how to solve the problem?
$ npm run dev
> info.zhaoyaojing.server-vue@1.0.0 dev /Library/WebServer/Documents/html/info.zhaoyaojing.server-vue
> webpack-dev-server --content-base ./ --open --inline --hot --compress --history-api-fallback --config webpack.dev.config.js
internal/modules/cjs/loader.js:596
throw err;
^
Error: Cannot find module "webpack"
at Function.Module._resolveFilename (internal/modules/cjs/loader.js:594:15)
at Function.Module._load (internal/modules/cjs/loader.js:520:25)
at Module.require (internal/modules/cjs/loader.js:650:17)
at require (internal/modules/cjs/helpers.js:20:18)
at Object.<anonymous> (/usr/local/lib/node_modules/webpack-dev-server/lib/Server.js:22:17)
at Module._compile (internal/modules/cjs/loader.js:702:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:713:10)
at Module.load (internal/modules/cjs/loader.js:612:32)
at tryModuleLoad (internal/modules/cjs/loader.js:551:12)
at Function.Module._load (internal/modules/cjs/loader.js:543:3)
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! info.zhaoyaojing.server-vue@1.0.0 dev: `webpack-dev-server --content-base ./ --open --inline --hot --compress --history-api-fallback --config webpack.dev.config.js`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the info.zhaoyaojing.server-vue@1.0.0 dev script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
npm ERR! A complete log of this run can be found in:
npm ERR! /Users/liwei/.npm/_logs/2018-06-16T06_53_36_187Z-debug.log