Error WorkflowScript: 8: Expected one of "steps", "stages", or "parallel" for stage "check out scm" when need to run a pipeline - jenkins

Question

I write this pipeline for run that after push on the develop branch or master branch and doing some workers related to that branch.
I want to check the repository and run pipeline after push on the any branches
pipeline {
triggers {
pollSCM('*/1 * * * * ')
}
agent any
stages {
stage('Check out scm') {
when {
branch 'master'
}
checkout scm
}
stage('Install npm') {
steps {
sh 'npm install'
}
}
stage('Build Project Develop') {
when {
branch 'develop'
}
steps {
sh 'ng build --prod '
}
}
stage('Build Project Realase')
{
when {
branch 'master'
}
steps {
sh 'ng build --prod '
}
}
stage('Move to Var') {
steps {
sh 'chown -R root:jenkins /var/lib/jenkins/workspace/Angular-CI-CD--Test_master/dist/ang-CICD/. && /var/www/html'
}
}
}
}
But it shows me this error:
Branch indexing
Connecting to https://api.github.com using kiadr9372/****** (GitHub Access Token)
Obtained Jenkinsfile from d57840a79c46a88969381cc978f378c7d6804cec
Running in Durability level: MAX_SURVIVABILITY
GitHub has been notified of this commit’s build result
org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
WorkflowScript: 8: Unknown stage section "checkout". Starting with version 0.5, steps in a stage must be in a ‘steps’ block. # line 8, column 9.
stage('check out scm') {
^
WorkflowScript: 8: Expected one of "steps", "stages", or "parallel" for stage "check out scm" # line 8, column 9.
stage('check out scm') {
^
What is the problem?

Answer 1

Solution
You need to place checkout scm within a step closure. You also have an additional closing bracket.
pipeline {
triggers {
pollSCM('*/1 * * * * ')
}
agent any
stages {
stage('check out scm') {
when {
branch 'master'
}
steps {
checkout scm
}
}
stage('Install npm') {
steps {
sh 'npm install'
}
}
stage('Build Project Develop') {
when {
branch 'develop'
}
steps {
sh 'ng build --prod '
}
}
stage('Build Project Realase') {
when {
branch 'master'
}
steps {
sh 'ng build --prod '
}
}
stage('Move to Var') {
steps {
sh 'chown -R root:jenkins /var/lib/jenkins/workspace/Angular-CI-CD--Test_master/dist/ang-CICD/. && /var/www/html'
}
}
}
}