Groovy script for Jenkins, for "Inject environment variables to the build process" to retrieve the version of the current package.json file (for NodeJs)

gistfile1.txt

import groovy.json.JsonSlurper
import jenkins.*
import jenkins.model.*
import hudson.*
import hudson.model.*

def build = Thread.currentThread().executable

def inputFile = new File(build.workspace.toString()  + "/package.json")
def InputJSON = new JsonSlurper().parseText(inputFile.text)

def map = [PACKAGE_VERSION: InputJSON.version] 
return map

Exposed as "PACKAGE_VERSION" environment variable