webpack-dev-server报错

错误

$ webpack-dev-server
D:\server\mmall-fe\node_modules\_ajv-keywords@2.1.1@ajv-keywords\keywords\instanceof.js:52
    throw new Error('invalid "instanceof" keyword value ' + c);
    ^

Error: invalid "instanceof" keyword value Promise
    at getConstructor (D:\server\mmall-fe\node_modules\_ajv-keywords@2.1.1@ajv-keywords\keywords\instanceof.js:52:11)
    at Ajv.compile (D:\server\mmall-fe\node_modules\_ajv-keywords@2.1.1@ajv-keywords\keywords\instanceof.js:21:27)
    at Object.useCustomRule (D:\server\mmall-fe\node_modules\_ajv@5.5.2@ajv\lib\compile\index.js:275:26)
    at Object.generate_custom [as code] (D:\server\mmall-fe\node_modules\_ajv@5.5.2@ajv\lib\dotjs\custom.js:32:24)
    at Object.generate_validate [as validate] (D:\server\mmall-fe\node_modules\_ajv@5.5.2@ajv\lib\dotjs\validate.js:347:35)
    at Object.generate_anyOf [as code] (D:\server\mmall-fe\node_modules\_ajv@5.5.2@ajv\lib\dotjs\anyOf.js:34:27)
    at generate_validate (D:\server\mmall-fe\node_modules\_ajv@5.5.2@ajv\lib\dotjs\validate.js:347:35)
    at localCompile (D:\server\mmall-fe\node_modules\_ajv@5.5.2@ajv\lib\compile\index.js:87:22)
    at Ajv.compile (D:\server\mmall-fe\node_modules\_ajv@5.5.2@ajv\lib\compile\index.js:56:13)
    at Ajv._compile (D:\server\mmall-fe\node_modules\_ajv@5.5.2@ajv\lib\ajv.js:358:27)

出现以上错误解决方案

以上问题是由于webpack-dev-server是由于版本问题造成的

重新安装版本

cnpm install webpack-dev-server@2.9.1 -g