npm WARN package.json: No repository field

I installed expressjs with the following command:

sudo npm install -g express

I have the following warning:

npm WARN package.json range-parser@0.0.4 No repository field.
npm WARN package.json fresh@0.1.0 No repository field.
npm WARN package.json methods@0.0.1 No repository field.
npm WARN package.json methods@0.0.1 No readme data.
npm WARN package.json cookie-signature@1.0.1 No repository field.
npm WARN package.json send@0.1.0 No repository field.
npm WARN package.json pause@0.0.1 No repository field.
npm WARN package.json bytes@0.2.0 No repository field.
npm WARN package.json github-url-from-git@1.1.1 No repository field.
npm WARN package.json assert-plus@0.1.2 No repository field.
npm WARN package.json ctype@0.5.2 No repository field.

Im new to nodejs and expressjs. Why I have the above warnings? Should I be worried?

It's just a check as of NPM v1.2.20, they report this as a warning.

However, don't worry, there are sooooooo many packages which still don't have the repository field in their package.json. The field is used for informational purposes.

In the case you're a package author, put the repository in your package.json, like this:

"repository": {
  "type": "git",
  "url": "git://github.com/username/repository.git"
}

Read more about the repository field, and see the logged bug for further details.

Additionally, as originally reported by @dan_nl, you can set private key in your package.json.
This will not only stop you from accidentally running npm publish in your app, but will also stop NPM from printing warnings.

{
  "name": "my-super-amazing-app",
  "version": "1.0.0",
  "private": true
}

you can also mark the application as private if you don’t plan to put it in an actual repository.

{
  "name": "my-application",
  "version": "0.0.1",
  "private": true
}

If you are getting this from your own package.json, just add the repository field to it. (use the link to your actual repository):

"repository" : { 
   "type" : "git",
   "url" : "http://github.com/npm/npm.git"
 }

As dan_nl stated, you can add a private fake repository in package.json. You don't even need name and version for it:

{
  ...,
  "repository": {
    "private": true
  }
}

Better still: Set the private flag directly. This way npm doesn't ask for a README file either:

{
  "name": ...,
  "description": ...,
  "version": ...,
  "private": true
}

This solution applies to windows platform, assuming you have installed every prerequisite.

  1. Open folder
  2. Right click in folder
  3. Select Create repository
  4. Open cmd prompt as administrator in this folder
  5. Type bower install

It will download bower_component and it should now work.

Have you run git init? That command runs you through everything...