Index: node_modules/d3-selection/src/selection/join.js
===================================================================
--- node_modules/d3-selection/src/selection/join.js	(revision e4c61dd6cd86e06265bc2bd91adba84a0f04044a)
+++ node_modules/d3-selection/src/selection/join.js	(revision e4c61dd6cd86e06265bc2bd91adba84a0f04044a)
@@ -0,0 +1,15 @@
+export default function(onenter, onupdate, onexit) {
+  var enter = this.enter(), update = this, exit = this.exit();
+  if (typeof onenter === "function") {
+    enter = onenter(enter);
+    if (enter) enter = enter.selection();
+  } else {
+    enter = enter.append(onenter + "");
+  }
+  if (onupdate != null) {
+    update = onupdate(update);
+    if (update) update = update.selection();
+  }
+  if (onexit == null) exit.remove(); else onexit(exit);
+  return enter && update ? enter.merge(update).order() : update;
+}