Cannot find module 'webpack'

> node build/dev-server.js
internal/modules/cjs/loader.js:651
    throw err;
    ^
Error: Cannot find module 'webpack'
    at Function.Module._resolveFilename (internal/modules/cjs/loader.js:649:15)
    at Function.Module._load (internal/modules/cjs/loader.js:575:25)
    at Module.require (internal/modules/cjs/loader.js:705:19)
    at require (internal/modules/cjs/helpers.js:14:16)
    at Object.<anonymous> (/Users/jiang/Documents/2019/项目/探索中心/code/bdcsc2x-portal-backend-page/build/dev-server.js:1:15)
    at Module._compile (internal/modules/cjs/loader.js:799:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:810:10)
    at Module.load (internal/modules/cjs/loader.js:666:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:606:12)
    at Function.Module._load (internal/modules/cjs/loader.js:598:3)
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! meeting-visl-page@1.0.0 dev: `node build/dev-server.js`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the meeting-visl-page@1.0.0 dev script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
npm WARN Local package.json exists, but node_modules missing, did you mean to install?
npm ERR! A complete log of this run can be found in:
npm ERR!     /Users/jiang/.npm/_logs/2019-10-15T02_48_55_006Z-debug.log