official notes on npmjs semver

syntax

• version Must match version exactly
• >version Must be greater than version
• >=version etc
• <version
• <=version
• ~version “Approximately equivalent to version” See semver ( via the external link above )
• ^version “Compatible with version” See semver
• 1.2.x 1.2.0, 1.2.1, etc., but not 1.3.0
• http://... See ‘URLs as Dependencies’ in the original page
• * Matches any version
• "" (just an empty string) Same as *
• version1 - version2 Same as >=version1 <=version2.
• range1 || range2 Passes if either range1 or range2 are satisfied.

valid examples

{ "dependencies" :
  { "foo" : "1.0.0 - 2.9999.9999"
  , "bar" : ">=1.0.2 <2.1.2"
  , "baz" : ">1.0.2 <=2.3.4"
  , "boo" : "2.0.1"
  , "qux" : "<1.0.0 || >=2.3.1 <2.4.5 || >=2.5.2 <3.0.0"
  , "asd" : "http://asdf.com/asdf.tar.gz"
  , "til" : "~1.2"
  , "elf" : "~1.2.3"
  , "two" : "2.x"
  , "thr" : "3.3.x"
  , "lat" : "latest"
  , "dyl" : "file:../dyl"
  }
}