1、查看当前的镜像地址

npm get registry

原镜像地址：
https://registry.npmjs.org/

设成淘宝的

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

将npm替换为cnpm

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

全局安装yarn

cnpm install yarn -g

2.换成原来的镜像地址

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