Fix #197 iterable selections.

src/selection/index.js

@@ -29,6 +29,7 @@ import selection_clone from "./clone";
 import selection_datum from "./datum";
 import selection_on from "./on";
 import selection_dispatch from "./dispatch";
+import selection_iterator from "./iterator";
 
 export var root = [null];
 
@@ -73,7 +74,8 @@ Selection.prototype = selection.prototype = {
   clone: selection_clone,
   datum: selection_datum,
   on: selection_on,
-  dispatch: selection_dispatch
+  dispatch: selection_dispatch,
+  [Symbol.iterator]: selection_iterator
 };
 
 export default selection;

src/selection/iterator.js

@@ -0,0 +1,7 @@
+export default function*() {
+  for (var groups = this._groups, j = 0, m = groups.length; j < m; ++j) {
+    for (var group = groups[j], i = 0, n = group.length, node; i < n; ++i) {
+      if (node = group[i]) yield node;
+    }
+  }
+}

test/selection/iterator-test.js

@@ -0,0 +1,27 @@
+var tape = require("tape"),
+    jsdom = require("../jsdom"),
+    d3 = require("../../");
+
+tape("selection are iterable over the selected nodes", function(test) {
+  var document = jsdom("<h1 id='one'></h1><h1 id='two'></h1>"),
+      one = document.querySelector("#one"),
+      two = document.querySelector("#two");
+  test.deepEqual([...d3.selectAll([one, two])], [one, two]);
+  test.end();
+});
+
+tape("selection iteration merges nodes from all groups into a single array", function(test) {
+  var document = jsdom("<h1 id='one'></h1><h1 id='two'></h1>"),
+      one = document.querySelector("#one"),
+      two = document.querySelector("#two");
+  test.deepEqual([...d3.selectAll([one, two]).selectAll(function() { return [this]; })], [one, two]);
+  test.end();
+});
+
+tape("selection iteration skips missing elements", function(test) {
+  var document = jsdom("<h1 id='one'></h1><h1 id='two'></h1>"),
+      one = document.querySelector("#one"),
+      two = document.querySelector("#two");
+  test.deepEqual([...d3.selectAll([, one,, two])], [one, two]);
+  test.end();
+});