use duck test for marks (#967)

mbostock · web-flow · commit 3371256ab6db · 2022-07-03T12:47:21.000-04:00
diff --git a/src/plot.js b/src/plot.js
@@ -307,7 +307,7 @@ export function marks(...marks) {
 }
 
 function markify(mark) {
-  return mark instanceof Mark ? mark : new Render(mark);
+  return typeof mark?.render === "function" ? mark : new Render(mark);
 }
 
 class Render extends Mark {

Original file line number	Diff line number	Diff line change
`@@ -307,7 +307,7 @@ export function marks(...marks) {`
`307`	`307`	`}`
`308`	`308`
`309`	`309`	`function markify(mark) {`
`310`		`- return mark instanceof Mark ? mark : new Render(mark);`
	`310`	`+ return typeof mark?.render === "function" ? mark : new Render(mark);`
`311`	`311`	`}`
`312`	`312`
`313`	`313`	`class Render extends Mark {`