onChange client script: show and require a field conditionally

A common form rule: when category is a certain value, ask for an extra detail. Try a UI Policy first; use a client script when the condition needs logic UI Policies can’t express.

function onChange(control, oldValue, newValue, isLoading, isTemplate) {
  var FIELD = 'u_hardware_asset_tag'; // the field to show and require
  var needed = newValue === 'hardware';

  g_form.setDisplay(FIELD, needed);
  g_form.setMandatory(FIELD, needed);

  if (!needed && !isLoading) {
    g_form.clearValue(FIELD); // don't leave hidden data behind
  }
}

How it works

• Runs on load and on every change of the watched field, so the form is always in the right state.
• setMandatory(false) before hiding means a hidden field can never block saving.

Gotchas

• If a UI Policy can do it, prefer the UI Policy: it’s declarative and easier for admins to maintain.
• Make sure the field is on the form (it can be hidden by default); client scripts can’t show fields that aren’t there.