使用create-react-app时遇到Module not found问题
本来项目跑的好好地，然后install了一个axios，然后项目就挂了。 各种Module not found，路径不对。 期初以为是可能丢包了，又重新install还是不行，根据错误提示一个个删一个个重新install。 最后干脆重新建了个项目，但仍然不行。 这时候意识到了问题应该是出在create-react-app上：
根据这个猜想，清空了packge卸载了全部model，重新install才解决问题。原因我现在也还不知道什么情况会触发这个bug，欢迎指教。
上代码：
-
npm install rimraf -g //安装删除指令
-
rimraf node_modules //卸载node库
-
npm install //重装
npm WARN deprecated fsevents windows
更新下 使用yarn貌似会帮助跳过这个问题：
info fsevents@2.1.2: The platform "win32" is incompatible with this module.
info "fsevents@2.1.2" is an optional dependency and failed compatibility check. Excluding it from installation.
info fsevents@1.2.9: The platform "win32" is incompatible with this module.
info "fsevents@1.2.9" is an optional dependency and failed compatibility check. Excluding it from installation.
===
有需要下载了一个模板项目，安装ui部分失败，提示：
npm WARN deprecated fsevents@1.2.9: One of your dependencies needs to upgrade to fsevents v2: 1) Proper nodejs v10+ support 2) No more fetch
ing binaries from AWS, smaller package size
npm ERR! Unexpected end of JSON input while parsing near '...LNCxGNsOAHRWRMGoXrtcI'
npm ERR! A complete log of this run can be found in:
npm ERR! C:UsersuserAppDataRoaming
pm-cache\_logs2019-12-06T07_31_31_687Z-debug.log
单独提出来安装：
$ npm install fsevents
npm ERR! code EBADPLATFORM
npm ERR! notsup Unsupported platform for fsevents@2.1.2: wanted {"os":"darwin","arch":"any"} (current: {"os":"win32","arch":"x64"})
npm ERR! notsup Valid OS: darwin
npm ERR! notsup Valid Arch: any
npm ERR! notsup Actual OS: win32
npm ERR! notsup Actual Arch: x64
npm ERR! A complete log of this run can be found in:
npm ERR! C:Users
eoliu6AppDataRoaming
pm-cache\_logs2019-12-06T07_33_23_843Z-debug.log
原因明了了，这个包是在mac系统中的，windows没有。查了下资料，大概是windows也不需要，不用安装。
解决方法是，把fsevents依赖放到可选依赖中：
vi package.json
"optionalDependencies": {
"fsevents": "*"
}
重新执行安装(有个坑，需要删除package_lock.json,否则标记会失效，所有依赖都将被安装):
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1
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npm install --no-optional |
参考资料：
https://stackoverflow.com/questions/41570364/npm-install-not-working-in-windows#
But it says it is optional so I ran $npm install --no-optional and that error went away but I still can't install.
https://github.com/npm/npm/issues/17633
I'm seeing this today with npm 5.3.0. npm install --no-optional works IIF a package-lock.json does not exist. If the package-lock.json file exists, then the flag is ignored and all dependencies get installed.
3.撤换taobao源后，使用create-reat-app命令生成的app,默认package.json文件中不带运行脚本命令如下：
（node: ver2.13.1 npm ver:6.12.1）
{
"name": "test",
"version": "0.1.0",
"private": true,
"dependencies": {
"react": "^16.12.0",
"react-dom": "^16.12.0",
"react-scripts": "3.3.0"
}
}
需要手动添加运行脚本代码如下：
{
"name": "test",
"version": "0.1.0",
"private": true,
"dependencies": {
"react": "^16.12.0",
"react-dom": "^16.12.0",
"react-scripts": "3.3.0"
},
"scripts": {
"start": "react-scripts start",
"build": "react-scripts build",
"test": "react-scripts test",
"eject": "react-scripts eject"
},
"eslintConfig": {
"extends": "react-app"
},
"browserslist": {
"production": [
">0.2%",
"not dead",
"not op_mini all"
],
"development": [
"last 1 chrome version",
"last 1 firefox version",
"last 1 safari version"
]
}
}
还有public,src等目录需要自己添加，当然业务代码需要自己编写哦
然后才能通过npm run start 命令才能运行项目。
使用系统默认源的配置信息如下：
npm config list
npm config list
; cli configs
metrics-registry = "https://registry.npmjs.org/"
scope = ""
user-agent = "npm/6.12.1 node/v12.13.1 win32 x64"
; userconfig C:UsersAdministrator.npmrc
cache = "c:\tmp\node_cache"
prefix = "c:\tmp\node_global"
如果使用taobo源，使用npm config list 查看配置信息如下：
; cli configs
metrics-registry = "https://registry.npm.taobao.org/"
scope = ""
user-agent = "npm/6.12.1 node/v12.13.1 win32 x64"
; userconfig C:UsersAdministrator.npmrc
cache = "c:\tmp\node_cache"
disturl = "https://npm.taobao.org/dist"
prefix = "c:\tmp\node_global"
registry = "https://registry.npm.taobao.org/"
经过测试对比发现，现在通过create-react-app命令生成的APP，没有原来带小卫星转的演示代码，现在只有
的库及其依赖库，可能是新版本取消原来的模板了，知道的网友请指教，谢谢。
如果生成的app是web应用程序，需要指定服务启动端口，可以在在package.json文件中配置"scripts“项中的start修改为如下
"scripts": {"start": "SET PORT & react-scripts start",
。。。。。。
即可改变默认服务器启动端口。