Page Comparison

import com.onresolve.scriptrunner.runner.customisers.WithPlugin;
import com.atlassian.jira.event.type.EventDispatchOption;
import com.atlassian.jira.component.ComponentAccessor;
import com.atlassian.jira.issue.MutableIssue;
@WithPlugin("com.okapya.jira.checklist")
import com.okapya.jira.customfields.*;

// Retrieve the Custom Field Type for the Checklist Custom Field
def customFieldManager = ComponentAccessor.getCustomFieldManager();
def checklistCustomField = customFieldManager.getCustomFieldObject("customfield_10013");
def checklistCustomFieldType = (ChecklistCFType) checklistCustomField.getCustomFieldType();

// Check all items
def issue = (MutableIssue) event.issue;
def ArrayList<ChecklistItem> existingChecklistValue = (ArrayList<ChecklistItem>) issue.getCustomFieldValue(checklistCustomField);
for (ChecklistItem item : existingChecklistValue) {
    item.setChecked(true);
}

// Update the issue with the checklist
def issueManager = ComponentAccessor.getIssueManager();
issue.setCustomFieldValue(checklistCustomField, existingChecklistValue.toList());
issueManager.updateIssue(event.user, issue, EventDispatchOption.ISSUE_UPDATED, false);