npm windows install globally results in npm ERR! extraneous
npm ERR! extraneous means a package is installed but is not listed in your project's package.json.
Since you're listing packages that have been installed globally, it's going to give you a lot of extraneous errors that can be simply ignored because most things installed globally will not be in your project's package.json.
1 & 2: It means you don't have the jshint listed in your project's package.json file but that it is globally installed. So it is not a big problem.
3: To avoid this extraneous error, you can run or re-run the install with the option --save . This will update automatically you package.json file :
npm install -g jshint --saveOr need to update manually your package.json file with a "dependencies": {...}