Get a user's manager via GlideAjax

GlideAjax exists because client scripts can't query the database directly — they need a server-side Script Include to act as a bridge. The critical mistake developers make is assuming the response will always contain valid data. Network failures, ACL denials, or missing records will return empty strings or 'null' literals that break reference field population. Always validate the response string before calling setValue(), and handle the empty case gracefully with user feedback.

When to use this pattern

• Client scripts need to populate reference fields based on current user context
• Form loads where manager assignment should be automatic but not mandatory
• Catalog items that need to pre-fill approval fields with user hierarchy data
• Custom forms where user can still override the suggested manager value

When NOT to use this pattern

• Server-side scripts (Business Rules, Script Actions) — use GlideRecord directly to avoid unnecessary HTTP overhead
• Mandatory field population — use onLoad() client scripts or Business Rules instead
• Bulk operations or list views — creates one AJAX call per row, use server-side processing
• Complex hierarchy traversal — use GlideAggregate or recursive Business Rules for performance

Key behaviors and gotchas

• Response validation is critical — empty responses return the string 'null' not JavaScript null
• Use manager.nil() not manager == '' — reference fields have specific empty-state behavior
• Script Includes inherit calling user's ACLs — users without sys_user read access will get empty responses
• Always check isLoading in onChange() — prevents AJAX calls during form initialization
• GlideAjax is asynchronous — don't chain dependent calls without proper callback nesting
• Domain separation applies to the Script Include execution context, not the client script