How to convert freestyle jenkins to jenkins scripted pipeline

Question

I am writing because for several weeks I have been struggling with rewriting the freestyle jenkins code that was executed in the / bin / bash shell on the pipeline. At the beginning, I was wondering what type of pipeline to choose, whether it is a declarative pipeline or a scripted pipeline. I chose the scripted pipeline because with this script I run gulp that the pipeline declarative would not have access to.

The first problem I encountered was the lack of a file in the $ {WORKSPACE}/artifacts directory for a given job, which I previously uploaded using the add file option:

this was not a problem in the freestyle pipeline.

Second problem, how should I write variables in the scripted pipeline is something like below correct ??

def artifacts_dir="\${WORKSPACE}/artifacts"
def artefact_dir= "\${WORKSPACE}/artifacts}"
def scfs_dir="\${WORKSPACE}/scf_migration_validator/scf_data/baseline/SBTS/"
def admin_trunk_dir="/home/jenkins/admin_repos/admin_trunk"
def cores=14


build_admin_html (dir, branch) {
  sh """
  #!/bin/bash
  set +x 
  touch rules.pdl
  echo Building admin HTML!
  cd ${dir}/admin
  cp ${artifacts_dir}/rules.pdl ${dir}/admin/admin-core/resources/pdlValidation/PDL/SRAN/
  gulp package --skip-wasm --svn-branch=${branch} --max-old-space-size=8192 --use-local --no-auth
  cp ${dir}/admin/.tmp/bundles/no-auth/ADMIN.html ${artifacts_dir}
  echo
  """
}


timestamps {

node ('local-docker') { 

    stage ('Build_Knife - Checkout') {
     checkout([$class: 'GitSCM', branches: [[name: '**']], doGenerateSubmoduleConfigurations: false, extensions: [], submoduleCfg: [], userRemoteConfigs: [[credentialsId: 'cab881bd-a4c4-41d8-aa9c-74a20d341903', url: '[email protected]:szmajdzi/pdl-testing.git']]]) 
    }
    stage ('Build_Knife - Build') {
    
    build_admin_html (admin_trunk_dir, 'trunk')
    
    }
   }
  }

I should write like this:

$ {artifacts_dir}
or so
\ $ {artifacts_dir}