1.查看当前镜像源

yarn config get registry

2.临时修改yarn源 

yarn save package_name --registry https://registry.npm.taobao.org/

3.修改yarn源为taobao源

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

4.修改yarn源为官方源

yarn config set registry https://registry.yarnpkg.com