Jenkins Pipeline Styles: Scripted VS Declarative

Jenkinsfile

pipeline {
    agent any

    environment {
        registry = 'https://my.registry.com'
        registryCredential = 'docker-registry-login'

        appName = 'application-name'
        appVersion = '1.0.0-RELEASE'

        dockerImage = ''
    }

    stages {
        stage('checkout') {
            steps {
                checkout scm
            }
        }

        stage('prepare') {
            steps {
                sh 'node --version'
                sh 'npm --version'
                sh 'ls -la'
            }
        }

        stage('image build') {
            steps {
                script {
                    dockerImage = docker.build('$appName:$appVersion')
                }
            }
        }

        stage('image publish') {
            steps {
                script {
                    docker.withRegistry(registry, registryCredential) {
                        dockerImage.push()
                    }
                }
            }
        }
    }

    post {
        success {
            sh 'echo success'
        }
        failure {
            sh 'echo failure'
        }
    }
}

Jenkinsfile-legacy

#!/usr/bin/env groovy

def version = '1.0.0-RELEASE'

node {
    stage('checkout') {
        checkout scm
    }

    stage('prepare') {
        sh "node --version"
        sh "npm --version"
        sh "ls -la"
    }

    def dockerImage
    stage('build image') {
        dockerImage = docker.build('application-name')
    }
    stage('publish image') {
        docker.withRegistry('https://my.registry.com', 'docker-registry-login') {
            dockerImage.push version
        }
    }
}