"n use" style command for invoking npm

[tjwebb]

n use <version> runs node as a particular version. I think it'd be useful to also be able to run npm in this manner as well. The CLI could then look something like:

1. install: $ n <version>
2. run node: $ n <version> node (or currently, $ n use <version>)
3. run npm: $ n <version> npm

[bfricka]

+1 This would be very useful. In its current incarnation, the results are weird. For example, this happened today:

# From v0.10.29
brew upgrade node
...
node -v
v0.10.30
npm -v
1.4.23

Then check n:

n # gets stuck in limbo b/c brew took over
n stable # Installs v0.10.30
node -v
v0.10.30
npm -v
1.4.23

Cool. Makes sense. But...

n latest
node -v
v0.11.13
npm -v
1.4.9

:(. Switch back

n stable
node -v
v0.10.30
npm -v
1.4.21 # F*ck

Thus, every n switch requires npm to be updated to the desired version.

[wprater]

this is a great idea for running scripts as a certain version. progress?

[bitdivine]

There is a sketch implementation of how this might work in #192

Usage:

n with <version> npm install

Code: https://github.com/bitdivine/n

This is not ready for merging into master but I find it useful to have a working implementation to play with to make sure that the feature implements all the goodies it promises.

[bitdivine]

Do the above semantics work for you? They are:

+    n npm <version> [args ...]     Execute npm with node <version> and [args ...]
+    n with <version> [command ...] Execute command with the given version of node at the front of the PATH.

If so I can make the implementation more robust and send you a pull request.

[shadowspawn]

I suggest following same syntax as nvs and nvm which both have an exec command:

n exec <version> [command ...]

So running npm could look like:

n exec lts npm --version

[shadowspawn]

This is not likely to make it to n anytime soon. I have implemented this in nvh if any readers would like to give it a try.

[shadowspawn]

Prerelease available via npm i n@next for v6. Release notes: https://github.com/tj/n/releases/tag/6.0.0-0

[shadowspawn]

Added n exec in v6: https://github.com/tj/n/releases/tag/v6.0.0