How do I check for compatibility between versions with the npm semver module?

Question

How do I check for compatibility between versions with the npm semver module?

Using the semver package I didn't see a simple way to check if I need a version of a library whether I have a compatible version. That made me wonder if I'm missing something obvious since it would seem like a common operation.

According to the Semver.org any version that is the same or new but is not in a new major version is supposed to be compatible. Therefore if I need 1.2.3 and I have >=1.2.3 <2.0.0 then it's all good. I can build that comparison by hand, it just seems so common that I'm curious if I'm missing a simpler way.

In other words, it appears I apparently have to do this

var canUse = function(need, have) { 
  var nextMajorVersion = semver.inc(need, 'major'); 
  return semver.satisfies(have, '>=' + need + ' && ' + '<' + nextMajorVersion); 
};

Which works

canUse('1.2.3', '1.2.3');  // true
canUse('1.2.3', '1.2.4');  // true
canUse('1.2.3', '1.3.0');  // true
canUse('1.2.3', '0.4.4');  // false
canUse('1.2.3', '2.4.4');  // false

Yes, it's a tiny piece of code. It just seemed like that would be such a common operation that I wouldn't have to manipulate strings and manually build a range comparison just to check what seems like it a common question, is X compatible with Y.

Is there an easier way?

node.js
semantic-versioning

Answer 1

The caret operator should create the expected range in most cases:

^1.2.3 := >=1.2.3-0 <2.0.0-0 "Compatible with 1.2.3". When using caret operators, anything from the specified version (including prerelease) will be supported up to, but not including, the next major version (or its prereleases). 1.5.1 will satisfy ^1.2.3, while 1.2.2 and 2.0.0-beta will not.

semver.satisfies('1.2.3', '^1.2.3') // true
semver.satisfies('1.2.4', '^1.2.3') // true
semver.satisfies('1.3.0', '^1.2.3') // true
semver.satisfies('0.4.4', '^1.2.3') // false
semver.satisfies('2.4.4', '^1.2.3') // false

The exception is with 0.x.x versions. For these, a ^ will be ignored.

^0.1.3 := 0.1.3 "Compatible with 0.1.3". 0.x.x versions are special: since the semver spec specifies that 0.x.x versions make no stability guarantees, only the version specified is considered valid.

semver.satisfies('0.8.9', '^0.1.0') // false