Bulk Update the Value of a Custom Field on Jira Cloud Work Items

// Specify all the required parameters
def spaceKey = 'TEST'
def customFieldName = 'Story Points'
def newCustomFieldValue = 100

// Extract work item key using JQL Query
WorkItems.search("project = $spaceKey and '${customFieldName}' is not EMPTY").each { workItem ->
    workItem.update  {
        setCustomFieldValue(customFieldName, newCustomFieldValue)
    }
}