安装webpack-dev-server后，npm run dev报错

> vuewebpack@1.0.0 dev F:\GitHub\vue\vueWebpack

> cross-env NODE_ENV=development webpack-dev-server --config webpack.config.js

F:\GitHub\vue\vueWebpack\node_modules\ajv-keywords\keywords\instanceof.js:52

throw new Error('invalid "instanceof" keyword value ' + c);

^

Error: invalid "instanceof" keyword value Promise

at getConstructor (F:\GitHub\vue\vueWebpack\node_modules\ajv-keywords\keywords\instanceof.js:52:11)

at Ajv.compile (F:\GitHub\vue\vueWebpack\node_modules\ajv-keywords\keywords\instanceof.js:21:27)

at Object.useCustomRule (F:\GitHub\vue\vueWebpack\node_modules\ajv\lib\compile\index.js:275:26)

at Object.generate_custom [as code] (F:\GitHub\vue\vueWebpack\node_modules\ajv\lib\dotjs\custom.js:32:24)

at Object.generate_validate [as validate] (F:\GitHub\vue\vueWebpack\node_modules\ajv\lib\dotjs\validate.js:347:35)

at Object.generate_anyOf [as code] (F:\GitHub\vue\vueWebpack\node_modules\ajv\lib\dotjs\anyOf.js:34:27)

at generate_validate (F:\GitHub\vue\vueWebpack\node_modules\ajv\lib\dotjs\validate.js:347:35)

at localCompile (F:\GitHub\vue\vueWebpack\node_modules\ajv\lib\compile\index.js:87:22)

at Ajv.compile (F:\GitHub\vue\vueWebpack\node_modules\ajv\lib\compile\index.js:56:13)

at Ajv._compile (F:\GitHub\vue\vueWebpack\node_modules\ajv\lib\ajv.js:358:27)

npm ERR! code ELIFECYCLE

npm ERR! errno 1

npm ERR! vuewebpack@1.0.0 dev: `cross-env NODE_ENV=development webpack-dev-server --config webpack.config.js`

npm ERR! Exit status 1

npm ERR!

npm ERR! Failed at the vuewebpack@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! C:\Users\Administrator\AppData\Roaming\npm-cache\_logs\2018-06-11T14_03_14_218Z-debug.log

解决：版本的影响