Require at least one method for 'ElementHandler'

leo-ar · jrf0110 · commit cb3dd6f23902 · 2020-04-10T15:00:03.000-05:00
Taken from the answer given by https://stackoverflow.com/users/2077574/kpd in https://stackoverflow.com/a/49725198
diff --git a/index.d.ts b/index.d.ts
@@ -307,7 +307,7 @@ interface Doctype {
   readonly systemId: string | null
 }
 
-interface ElementHandler {
+interface ElementHandlerOptionals {
   /**
    * An incoming element, such as `div`
    */
@@ -322,6 +322,15 @@ interface ElementHandler {
   text?(text: Text): void
 }
 
+// See https://stackoverflow.com/a/49725198
+type RequireAtLeastOne<T, Keys extends keyof T = keyof T> =
+  Pick<T, Exclude<keyof T, Keys>>
+  & {
+    [K in Keys]-?: Required<Pick<T, K>> & Partial<Pick<T, Exclude<Keys, K>>>
+  }[Keys]
+
+type ElementHandler = RequireAtLeastOne<ElementHandlerOptionals, 'element' | 'comments' | 'text'>
+
 interface DocumentHandler {
   /**
    * An incoming doctype, such as <!DOCTYPE html>
