Index: node_modules/d3-transition/src/transition/styleTween.js
===================================================================
--- node_modules/d3-transition/src/transition/styleTween.js	(revision e4c61dd6cd86e06265bc2bd91adba84a0f04044a)
+++ node_modules/d3-transition/src/transition/styleTween.js	(revision e4c61dd6cd86e06265bc2bd91adba84a0f04044a)
@@ -0,0 +1,24 @@
+function styleInterpolate(name, i, priority) {
+  return function(t) {
+    this.style.setProperty(name, i.call(this, t), priority);
+  };
+}
+
+function styleTween(name, value, priority) {
+  var t, i0;
+  function tween() {
+    var i = value.apply(this, arguments);
+    if (i !== i0) t = (i0 = i) && styleInterpolate(name, i, priority);
+    return t;
+  }
+  tween._value = value;
+  return tween;
+}
+
+export default function(name, value, priority) {
+  var key = "style." + (name += "");
+  if (arguments.length < 2) return (key = this.tween(key)) && key._value;
+  if (value == null) return this.tween(key, null);
+  if (typeof value !== "function") throw new Error;
+  return this.tween(key, styleTween(name, value, priority == null ? "" : priority));
+}