Add method to test if tag is a pre-release tag

[SamyPesse]

It'd be great to have a method like semver.isPrerelease(v):

> semver.isPrerelease("1.0.0")
false

> semver.isPrerelease("1.0.0-alpha.1")
true

[SamyPesse]

And maybe have a method to extract the type of prerelease:

> semver.prerelease("1.0.0-alpha.1") // or semver.pre ?
"alpha"

> semver.prerelease("1.0.0-beta.45")
"beta"

[isaacs]

Shouldn't it return the full "alpha.1" or "beta.45"?

Another option would be to return the full parsed prerelease field if it's there, or else null. Maybe something like this?

> require('semver').parse('1.2.3-alpha.23.bravo.43').prerelease
[ 'alpha', 23, 'bravo', 43 ]
> require('semver').parse('1.2.3').prerelease
[]
> function prerelease (ver) { var p = require('semver').parse(ver); return p && p.prerelease.length && p.prerelease || null }
undefined
> prerelease('1.2.3-alpha.4.bravo.65')
[ 'alpha', 4, 'bravo', 65 ]
> prerelease('1.2.3')
null

[SamyPesse]

Something like this would be perfect 👍

You're right, it should return the full parsed prerelease, since there is no strict convention on the prerelease's format: some people are using alpha.x and some others are using numerical values like 1.0.0-0.3.7; and others are using the pre-release part as a patch (ex: https://github.com/nwjs/npm-installer#install-a-specific-version-of-nwjs).

I was trying to find the most conventional way to filter versions by "pre-release's category" (stable, beta, alpha, ..) for Nuts. I'll probably consider that pre-release like 1.0.0-0.3.7 are alpha.

[luckydrq]

I have the same demand. Any update on this?