我輸入打包命令 webpack 為什么沒有打包成功，報錯信息為：

D:\webpack-test>webpack

C:\Users\Administrator\node_modules\webpack-cli\bin\cli.js:244

? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? throw err;

? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ^

Error: Cannot find module 'webpack'

? ? at Function.Module._resolveFilename (internal/modules/cjs/loader.js:581:15)

? ? at Function.Module._load (internal/modules/cjs/loader.js:507:25)

? ? at Module.require (internal/modules/cjs/loader.js:637:17)

? ? at require (C:\Users\Administrator\node_modules\v8-compile-cache\v8-compile-

cache.js:159:20)

? ? at Object.<anonymous> (C:\Users\Administrator\node_modules\webpack-cli\bin\c

onvert-argv.js:7:24)

? ? at Module._compile (C:\Users\Administrator\node_modules\v8-compile-cache\v8-

compile-cache.js:178:30)

? ? at Object.Module._extensions..js (internal/modules/cjs/loader.js:700:10)

? ? at Module.load (internal/modules/cjs/loader.js:599:32)

? ? at tryModuleLoad (internal/modules/cjs/loader.js:538:12)

? ? at Function.Module._load (internal/modules/cjs/loader.js:530:3)

? ? at Module.require (internal/modules/cjs/loader.js:637:17)

? ? at require (internal/modules/cjs/helpers.js:22:18)

? ? at yargs.parse (C:\Users\Administrator\node_modules\webpack-cli\bin\cli.js:2

41:14)

? ? at Object.parse (C:\Users\Administrator\node_modules\webpack-cli\node_module

s\yargs\yargs.js:563:18)

? ? at C:\Users\Administrator\node_modules\webpack-cli\bin\cli.js:219:8

? ? at Object.<anonymous> (C:\Users\Administrator\node_modules\webpack-cli\bin\c

li.js:530:3)

? ? at Module._compile (internal/modules/cjs/loader.js:689:30)

? ? at Object.Module._extensions..js (internal/modules/cjs/loader.js:700:10)

? ? at Module.load (internal/modules/cjs/loader.js:599:32)

? ? at tryModuleLoad (internal/modules/cjs/loader.js:538:12)

? ? at Function.Module._load (internal/modules/cjs/loader.js:530:3)

? ? at Module.require (internal/modules/cjs/loader.js:637:17)

? ? at require (internal/modules/cjs/helpers.js:22:18)

? ? at Object.<anonymous> (C:\Users\Administrator\AppData\Roaming\npm\node_modul

es\webpack\bin\webpack.js:155:2)

? ? at Module._compile (internal/modules/cjs/loader.js:689:30)

? ? at Object.Module._extensions..js (internal/modules/cjs/loader.js:700:10)

? ? at Module.load (internal/modules/cjs/loader.js:599:32)

? ? at tryModuleLoad (internal/modules/cjs/loader.js:538:12)

? ? at Function.Module._load (internal/modules/cjs/loader.js:530:3)

? ? at Function.Module.runMain (internal/modules/cjs/loader.js:742:12)