Index: node_modules/d3-selection/src/selection/selectChild.js
===================================================================
--- node_modules/d3-selection/src/selection/selectChild.js	(revision e4c61dd6cd86e06265bc2bd91adba84a0f04044a)
+++ node_modules/d3-selection/src/selection/selectChild.js	(revision e4c61dd6cd86e06265bc2bd91adba84a0f04044a)
@@ -0,0 +1,18 @@
+import {childMatcher} from "../matcher.js";
+
+var find = Array.prototype.find;
+
+function childFind(match) {
+  return function() {
+    return find.call(this.children, match);
+  };
+}
+
+function childFirst() {
+  return this.firstElementChild;
+}
+
+export default function(match) {
+  return this.select(match == null ? childFirst
+      : childFind(typeof match === "function" ? match : childMatcher(match)));
+}