How can you quickly check if you package.json file has modules that could be updated to newer versions?

Yes there is an option :

npm outdated

This will list modules, with available updates. It supports syntax for specifying the module name.

According to the Documentation, the syntax is

npm outdated [<name> [<name> ...]]

This gives you to specify the module name you wish to check exclusively, like

$ npm outdated mongoose

Note

To use this properly, you'll have to add a version number of the target module(s) with range greater than or greater than or equal. You can check node-semver, which is integrated into npm to check the syntax.

Example

{
    "dependencies": {
        "express": "3.2.0",
        "mongoose": ">= 3.5.6",
    },
}

Will give the following result ( since today the latest mongoose version is 3.6.9 )

$ npm outdated
...
mongoose@3.6.9 node_modules/mongoose current=3.6.7
$

While if you place

{
    "dependencies": {
        "express": ">= 3.2.0",
        "mongoose": ">= 3.5.6",
    },
}

The result will be :

$ npm outdated
...
mongoose@3.6.9 node_modules/mongoose current=3.6.7
express@3.2.3 node_modules/express current=3.2.0
$

there's a service like travis that checks it automatically:

https://gemnasium.com

you need to do that manually using the update command:

$ npm update

you can also change the version:

"nodemailer": "*" // this would use the newest version

or

"nodemailer": ">=0.4.0" // this will install any version which is at least 0.4.0

and so on....

read more about that here: https://npmjs.org/doc/json.html#dependencies

EDIT: there is some possibility if the module is available via github. you can then "watch" that repo, and get notification updates!

You might want to check out https://david-dm.org/ as it is free service that does the check. This is more target at adding a build badge to your README, but the details it gives on the page are quite helpful.

See https://david-dm.org/jshint/jshint as an example output.