Error report:

The CLI moved into a separate package: webpack-cli.
Please install 'webpack-cli' in addition to webpack itself to use the CLI.
-> When using npm: npm install webpack-cli -D
-> When using yarn: yarn add webpack-cli -D
module.js:442
    throw err;
    ^

Error: Cannot find module 'webpack-cli/bin/config-yargs'
    at Function.Module._resolveFilename (module.js:440:15)
    at Function.Module._load (module.js:388:25)
    at Module.require (module.js:468:17)
    at require (internal/module.js:20:19)
    at Object. (D:[email protected]@webpack-dev-serverbinwebpack-dev-server.js:6
5:1)
    at Module._compile (module.js:541:32)
    at Object.Module._extensions..js (module.js:550:10)
    at Module.load (module.js:458:32)
    at tryModuleLoad (module.js:417:12)
    at Function.Module._load (module.js:409:3)

npm ERR! Windows_NT 6.1.7601
npm ERR! argv "C:\Program Files\nodejs\node.exe" "C:\Program Files\nodejs\node_modules\npm\bin\npm-cli.js" "run
" "server"
npm ERR! node v6.2.1
npm ERR! npm  v3.9.3
npm ERR! code ELIFECYCLE
npm ERR! @ server: `webpack-dev-server --open`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the @ server script 'webpack-dev-server --open'.
npm ERR! Make sure you have the latest version of node.js and npm installed.
npm ERR! If you do, this is most likely a problem with the  package,
npm ERR! not with npm itself.
npm ERR! Tell the author that this fails on your system:
npm ERR!     webpack-dev-server --open
npm ERR! You can get information on how to open an issue for this project with:
npm ERR!     npm bugs
npm ERR! Or if that isn't available, you can get their info via:
npm ERR!     npm owner ls
npm ERR! There is likely additional logging output above.

npm ERR! Please include the following file with any support request:
npm ERR!     D:wabgnpm-debug.log

The reason:
Webpack is not compatible with the webpack-dev-server version, resulting in a compilation error.
Solution:
Uninstall and reinstall with the following command:
Uninstall version:

cnpm uninstall webpack -g   or    npm uninstall webpack -g
cnpm uninstall -g webpack-dev-server   or   npm uninstall -g webpack-dev-server

Install the specified version

cnpm install [email protected] --save-dev   or   npm install [email protected] --save-dev
cnpm install [email protected] --save -dev   or   npm install [email protected] --save -dev