很多时候我们都会根据需要去切换源，但是淘宝镜像一般都会在install的时候出一些错误，此时就需要切源：
一： 淘宝镜像：

临时使用：

npm --registry https://registry.npm.taobao.org install express

持久使用：

npm config set registry https://registry.npm.taobao.org

使用cnpm：

npm install -g cnpm --registry https://registry.npm.taobao.org

二： 使用官方镜像：

npm config set registry https://registry.npmjs.org/

使用nrm -- NPM registry 管理工具

Install
npm install -g nrm
Example

$ nrm ls

* npm ---- https://registry.npmjs.org/
  cnpm --- http://r.cnpmjs.org/
  taobao - https://registry.npm.taobao.org/
  nj ----- https://registry.nodejitsu.com/
  npmMirror  https://skimdb.npmjs.com/registry/
  edunpm - http://registry.enpmjs.org/

PS C:\Users\link\Desktop\WebSocket> nrm ls

  npm -------- https://registry.npmjs.org/       
  yarn ------- https://registry.yarnpkg.com/     
  cnpm ------- http://r.cnpmjs.org/
* taobao ----- https://registry.npm.taobao.org/  
  nj --------- https://registry.nodejitsu.com/   
  npmMirror -- https://skimdb.npmjs.com/registry/
  edunpm ----- http://registry.enpmjs.org/    

PS C:\Users\link\Desktop\WebSocket> nrm use npm 

   Registry has been set to: https://registry.npmjs.org/


PS C:\Users\link\Desktop\WebSocket> nrm ls    查询npm
* npm -------- https://registry.npmjs.org/       
  yarn ------- https://registry.yarnpkg.com/     
  cnpm ------- http://r.cnpmjs.org/
  taobao ----- https://registry.npm.taobao.org/  
  nj --------- https://registry.nodejitsu.com/   
  npmMirror -- https://skimdb.npmjs.com/registry/
  edunpm ----- http://registry.enpmjs.org/       

PS C:\Users\link\Desktop\WebSocket> nrm use taobao

   Registry has been set to: https://registry.npm.taobao.org/

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