Jenkinsfile: parameter precedence - jenkins

Question

Say I have a Jenkinsfile with stages based on a conditional such as the following. Then, in the Jenkins UI for a particular Pipeline Project, I may or may not have a (Global Variable String Parameter) parameter named CITY defined for a particular job.
If the CITY parameter is defined in the Jenkins project in the UI, I'd like it to use whatever city the user inputs. If the user doesn't input anything, I'd like it to default to a value in "Global Properties" (in "Manage Jenkins > Configure System > Global Properties")
If the CITY parameter is NOT defined in the UI (like if someone forgot to define that parameter in the Pipeline Project UI), I'd like it to somehow default to a value defined in the Jenkinsfile.
Simply put, I'd like to define a default in the Jenkinsfile such that if someone forgets to configure a Global Variable String Parameter in the Job UI, the default will be used.
I'm pretty new to Jenkins and Groovy, I'm not quite sure how to do this. How can I go about defining a default parameter in a Jenkinsfile that can be overridden by user input in the UI or a default from "Global Properties"? Any advice is appreciated.
pipeline {
agent any
stages {
stage('Always') {
steps {
script {
sh 'echo Welcome CITY=$CITY'
}
}
stage('Chicago') {
when {
expression {
params.CITY == "CHICAGO"
}
}
steps {
script {
sh 'echo Welcome to Chicago "CITY=$CITY"'
}
}
}
stage('NYC') {
when {
expression {
params.CITY == "NYC"
}
}
steps {
script {
sh 'echo Welcome to NYC "CITY=$CITY"'
}
}
}
}
}

Answer 1

there is no need to declare each city just add a string parameter with a default value and create a single stage that will take the default parameter if the user did not enter one
if this works for you please mark answer as correct :-)
pipeline {
agent any
parameters {
string(name: 'CITY', defaultValue: 'TEL_AVIV', description: 'this is the default if user dosnt enter parameter in the UI')
}
stages {
stage('CITY') {
steps {
script {
sh 'echo Welcome $CITY'
}
}
}
}
}