fix(babel): cumsum

[theonetheycallneo]

Hi! 👋

Firstly, thanks for your work on this project! 🙂

Today I used patch-package to patch d3-array@2.12.1 for the project I'm working on.

Here is the diff that solved my problem:

diff --git a/node_modules/d3-array/dist/d3-array.js b/node_modules/d3-array/dist/d3-array.js
index ec6ae78..afd592b 100644
--- a/node_modules/d3-array/dist/d3-array.js
+++ b/node_modules/d3-array/dist/d3-array.js
@@ -134,11 +134,18 @@ function cross(...values) {
 }
 
 function cumsum(values, valueof) {
-  var sum = 0, index = 0;
-  return Float64Array.from(values, valueof === undefined
-    ? v => (sum += +v || 0)
-    : v => (sum += +valueof(v, index++, values) || 0));
-}
+  let fn = (v) => (sum += +valueof(v, index++, values) || 0)
+  if (valueof === undefined) fn = (v) => (sum += +v || 0)
+  var sum = 0,
+    index = 0
+  return Float64Array.from(values, fn)
+}
+// function cumsum(values, valueof) {
+//   var sum = 0, index = 0;
+//   return Float64Array.from(values, valueof === undefined
+//     ? v => (sum += +v || 0)
+//     : v => (sum += +valueof(v, index++, values) || 0));
+// }
 
 function descending(a, b) {
   return b < a ? -1 : b > a ? 1 : b >= a ? 0 : NaN;

This issue body was partially generated by patch-package.

[mbostock]

Duplicate of #147.