Hello @kartik,
First check your NPM version
npm -v
1).Update NPM to current version:
View curent NPM version:
npm view npm version
Update npm to current version:
npm i -g npm
2). List all available NPM versions and make a custom install/update/roll-back
View all versions including "alpha", "beta" and "rc" (release candidate)
npm view npm versions --json
Reinstall NPM to a specific version chosen from the versions list - for example to 5.0.3
npm i -g npm@5.0.3
Hope this works!!
Thank You!!