npm can not install any package of solutions

1, execution

npm config get proxy

npm config get https-proxy

2, if the return value is not null, continue

npm config set proxy null

npm config set https-proxy null

3, execution

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

　　At this time, .npmrc disk file under c will the registry value is modified:

　　　　registry=http://registry.cnpmjs.org/