Index: node_modules/d3-array/src/extent.js
===================================================================
--- node_modules/d3-array/src/extent.js	(revision e4c61dd6cd86e06265bc2bd91adba84a0f04044a)
+++ node_modules/d3-array/src/extent.js	(revision e4c61dd6cd86e06265bc2bd91adba84a0f04044a)
@@ -0,0 +1,29 @@
+export default function extent(values, valueof) {
+  let min;
+  let max;
+  if (valueof === undefined) {
+    for (const value of values) {
+      if (value != null) {
+        if (min === undefined) {
+          if (value >= value) min = max = value;
+        } else {
+          if (min > value) min = value;
+          if (max < value) max = value;
+        }
+      }
+    }
+  } else {
+    let index = -1;
+    for (let value of values) {
+      if ((value = valueof(value, ++index, values)) != null) {
+        if (min === undefined) {
+          if (value >= value) min = max = value;
+        } else {
+          if (min > value) min = value;
+          if (max < value) max = value;
+        }
+      }
+    }
+  }
+  return [min, max];
+}