Here is the code change.
<execution>
<id>update-version</id>
<phase>generate-sources</phase>
<goals>
<goal>execute</goal>
</goals>
<configuration>
<properties>
<property>
<name>projectBaseDir</name>
<value>${project.basedir}</value>
</property>
<property>
<name>mavenVersion</name>
<value>${project.version}</value>
</property>
</properties>
<scripts>
<script>${project.basedir}/build/update-version.groovy</script>
</scripts>
</configuration>
</execution>
// ./build/update-version.groovy
def versionForJs = mavenVersion.replace("-SNAPSHOT", "-alpha1")
def file = new
File("${projectBaseDir}/src/main/javascript/gremlin-javascript/package.json")
file.write(file.getText("UTF-8").replaceFirst(/"version": "(.*)",/,
"\"version\": \"" + versionForJs + "\","))
