Simply change every dependency's version to *, then run npm update --save.

  "dependencies": {
    "express": "*",
    "mongodb": "*",
    "underscore": "*",
    "rjs": "*",
    "jade": "*",
    "async": "*"
  }

After:

  "dependencies": {
    "express": "~3.2.0",
    "mongodb": "~1.2.14",
    "underscore": "~1.4.4",
    "rjs": "~2.10.0",
    "jade": "~0.29.0",
    "async": "~0.2.7"
  }

Of course, this is the blunt hammer of updating dependencies. It's fine if—as you said—the project is empty and nothing can break.

On the other hand, if you're working in a more mature project, you probably want to verify that there are no breaking changes in your dependencies before upgrading.

To see which modules are outdated, just run npm outdated. It will list any installed dependencies that have newer versions available.

npm-check-updates is a utility that automatically adjusts a package.json with the latest version of all dependencies

see https://www.npmjs.org/package/npm-check-updates

$ npm install -g npm-check-updates
$ npm-check-updates -u
$ npm install 

To update one dependency to its lastest version without having to manually open the package.json and change it, you can run

npm install {package-name}@* {save flags?}

i.e.

npm install express@* --save

For reference, npm-install

PS: I also hate having to manually edit package.json for things like that ;)

This works as of npm 1.3.15.

"dependencies": {
  "foo": "latest"
}

The only caveat I have found with the best answer above is that it updates the modules to the latest version. This means it could update to an unstable alpha build.

I would use that npm-check-updates utility. My group used this tool and it worked effectively by installing the stable updates.

As Etienne stated above: install and run with this:

$ npm install -g npm-check-updates
$ npm-check-updates -u
$ npm install 

I recently had to update several projects that were using npm and package.json for their gruntfile.js magic. The following bash command (multiline command) worked well for me:

npm outdated --json --depth=0 | \
jq --ascii-output --monochrome-output '. | keys | .[]' | \
xargs npm install $1 --save-dev

The idea here: To pipe the npm outdated output as json, to jq
(jq is a json command line parser/query tool)
(notice the use of --depth argument for npm outdated)
jq will strip the output down to just the top level package name only.
finally xargs puts each LIBRARYNAME one at a time into a npm install LIBRARYNAME --save-dev command

The above is what worked for me on a machine runnning: node=v0.11.10 osx=10.9.2 npm=1.3.24

this required:
xargs http://en.wikipedia.org/wiki/Xargs (native to my machine I believe)
and
jq http://stedolan.github.io/jq/ (I installed it with brew install jq)

Note: I only save the updated libraries to package.json inside of the json key devDependancies by using --save-dev, that was a requirement of my projects, quite possible not yours.

Afterward I check that everything is gravy with a simple

npm outdated --depth=0

Also, you can check the current toplevel installed library versions with

npm list --depth=0

1. Use * as version definition for the latest version including unstable ones
2. Use latest as version definition for the latest stable version
3. Modify the package.json with exactly the latest stable version number using LatestStablePackages

Here is an example:

"dependencies": {
        "express": "latest"  // using the latest STABLE version
    ,   "node-gyp": "latest"    
    ,   "jade": "latest"
    ,   "mongoose": "*" // using the newest version, may involve the unstable one
    ,   "cookie-parser": "latest"
    ,   "express-session": "latest"
    ,   "body-parser": "latest"
    ,   "nodemailer":"latest"
    ,   "validator": "latest"
    ,   "bcrypt": "latest"
    ,   "formidable": "latest"
    ,   "path": "latest"
    ,   "fs-extra": "latest"
    ,   "moment": "latest"
    ,   "express-device": "latest"
},

The above commands are unsafe because you might break your module when switching versions. Instead I recommend the following

• Set actual current node modules version into package.json using npm shrinkwrap command.
• Update each dependency to the latest version IF IT DOES NOT BREAK YOUR TESTS using https://github.com/bahmutov/next-update command line tool

npm install -g next-update
// from your package
next-update

Use npm-check-updates and npm shrinkwrap

For the curious who make it this far, here is what I recommend:

Use npm-check-updates to suggest the latest versions.

$ npm install -g npm-check-updates
$ npm-check-updates

Install them if you agree

$ npm-check-updates -u

Then do a clean install (w/o the rm I got some dependency warnings)

$ rm -rf node_modules
$ npm install 

Now save your exact current module versions with npm shrinkwrap

$ rm npm-shrinkwrap.json
$ npm shrinkwrap

Now, when someone does a npm install on your project, they will always have the exact same packages as when you ran npm shrinkwrap.

npm-check-updates, npm shrinkwrap

If you're working in Visual Studio -

If you created the package.json file through Visual Studio, npm will not update your dependencies because of the file format.

problem: Creating a file in Visual Studio will use "Encode in UTF-8".

solution: Create the file in Notepad++, or some other editing app, and choose "Encode in ANSI" for the Encoding. In Notepad++ --> Select 'Encoding' from the menu --> Select 'Encode in ANSI'. Once the file is created, go into VS and 'Add Existing File' to your project. It should now work as desired.

Here's where I found the info:
http://racingcow.wordpress.com/2012/10/

Alternative is

"dependencies":{
    "foo" : ">=1.4.5"
}

everytime you use npm update , it automatically update to the latest version. For more version syntax, you may check here: https://www.npmjs.org/doc/misc/semver.html