From aa95e77d8761f34ea87f6af9ca89376e19d60c29 Mon Sep 17 00:00:00 2001
From: Mike Bostock <mbostock@gmail.com>
Date: Wed, 28 Feb 2018 10:45:15 -0800
Subject: [PATCH] Add transition.end. Fixes #77.

---
 .eslintrc               | 3 +++
 src/transition/end.js   | 9 +++++++++
 src/transition/index.js | 4 +++-
 3 files changed, 15 insertions(+), 1 deletion(-)
 create mode 100644 src/transition/end.js

diff --git a/.eslintrc b/.eslintrc
index d1da9f4..35c67db 100644
--- a/.eslintrc
+++ b/.eslintrc
@@ -1,6 +1,9 @@
 parserOptions:
     sourceType: module
 
+env:
+    es6: true
+
 extends:
     "eslint:recommended"
 
diff --git a/src/transition/end.js b/src/transition/end.js
new file mode 100644
index 0000000..55204d0
--- /dev/null
+++ b/src/transition/end.js
@@ -0,0 +1,9 @@
+// TODO Anonymous names for event listeners.
+export default function() {
+  var that = this, size = that.size();
+  return new Promise(function(resolve, reject) {
+    that.on("cancel.end interrupt.end", reject).on("end.end", function() {
+      if (--size === 0) resolve();
+    });
+  });
+}
diff --git a/src/transition/index.js b/src/transition/index.js
index b479b9f..ffb49ea 100644
--- a/src/transition/index.js
+++ b/src/transition/index.js
@@ -16,6 +16,7 @@ import transition_styleTween from "./styleTween";
 import transition_text from "./text";
 import transition_transition from "./transition";
 import transition_tween from "./tween";
+import transition_end from "./end";
 
 var id = 0;
 
@@ -60,5 +61,6 @@ Transition.prototype = transition.prototype = {
   tween: transition_tween,
   delay: transition_delay,
   duration: transition_duration,
-  ease: transition_ease
+  ease: transition_ease,
+  end: transition_end
 };