diff --git a/.eslintrc.json b/.eslintrc.json
index c2bd6c5..4b9180a 100644
--- a/.eslintrc.json
+++ b/.eslintrc.json
@@ -4,6 +4,9 @@
     "sourceType": "module",
     "ecmaVersion": 8
   },
+  "env": {
+    "es6": true
+  },
   "rules": {
     "no-cond-assign": 0,
     "no-constant-condition": 0
diff --git a/README.md b/README.md
index 0a930a2..510b64d 100644
--- a/README.md
+++ b/README.md
@@ -34,14 +34,14 @@ const tree = d3.quadtree();
 
 <a name="quadtree" href="#quadtree">#</a> d3.<b>quadtree</b>([<i>data</i>[, <i>x</i>, <i>y</i>]]) [<>](https://github.com/d3/d3-quadtree/blob/master/src/quadtree.js "Source")
 
-Creates a new, empty quadtree with an empty [extent](#quadtree_extent) and the default [*x*-](#quadtree_x) and [*y*-](#quadtree_y)accessors. If *data* is specified, [adds](#quadtree_addAll) the specified array of data to the quadtree. This is equivalent to:
+Creates a new, empty quadtree with an empty [extent](#quadtree_extent) and the default [*x*-](#quadtree_x) and [*y*-](#quadtree_y)accessors. If *data* is specified, [adds](#quadtree_addAll) the specified iterable of data to the quadtree. This is equivalent to:
 
 ```js
 const tree = d3.quadtree()
     .addAll(data);
 ```
 
-If *x* and *y* are also specified, sets the [*x*-](#quadtree_x) and [*y*-](#quadtree_y) accessors to the specified functions before adding the specified array of data to the quadtree, equivalent to:
+If *x* and *y* are also specified, sets the [*x*-](#quadtree_x) and [*y*-](#quadtree_y) accessors to the specified functions before adding the specified iterable of data to the quadtree, equivalent to:
 
 ```js
 const tree = d3.quadtree()
@@ -88,7 +88,7 @@ Adds the specified *datum* to the quadtree, deriving its coordinates ⟨*x*,*y*
 
 <a name="quadtree_addAll" href="#quadtree_addAll">#</a> <i>quadtree</i>.<b>addAll</b>(<i>data</i>) [<>](https://github.com/d3/d3-quadtree/blob/master/src/add.js "Source")
 
-Adds the specified array of *data* to the quadtree, deriving each element’s coordinates ⟨*x*,*y*⟩ using the current [*x*-](#quadtree_x) and [*y*-](#quadtree_y)accessors, and return this quadtree. This is approximately equivalent to calling [*quadtree*.add](#quadtree_add) repeatedly:
+Adds the specified iterable of *data* to the quadtree, deriving each element’s coordinates ⟨*x*,*y*⟩ using the current [*x*-](#quadtree_x) and [*y*-](#quadtree_y)accessors, and return this quadtree. This is approximately equivalent to calling [*quadtree*.add](#quadtree_add) repeatedly:
 
 ```js
 for (let i = 0, n = data.length; i < n; ++i) {
diff --git a/src/add.js b/src/add.js
index 985adfc..3d7c6ba 100644
--- a/src/add.js
+++ b/src/add.js
@@ -48,18 +48,14 @@ function add(tree, x, y, d) {
 }
 
 export function addAll(data) {
-  var d, i, n = data.length,
-      x,
-      y,
-      xz = new Array(n),
-      yz = new Array(n),
-      x0 = Infinity,
-      y0 = Infinity,
-      x1 = -Infinity,
-      y1 = -Infinity;
+  if (!Array.isArray(data)) data = Array.from(data);
+  const n = data.length;
+  const xz = new Float64Array(n);
+  const yz = new Float64Array(n);
+  let x0 = Infinity, y0 = x0, x1 = -x0, y1 = x1;
 
   // Compute the points and their extent.
-  for (i = 0; i < n; ++i) {
+  for (let i = 0, d, x, y; i < n; ++i) {
     if (isNaN(x = +this._x.call(null, d = data[i])) || isNaN(y = +this._y.call(null, d))) continue;
     xz[i] = x;
     yz[i] = y;
@@ -76,7 +72,7 @@ export function addAll(data) {
   this.cover(x0, y0).cover(x1, y1);
 
   // Add the new points.
-  for (i = 0; i < n; ++i) {
+  for (let i = 0; i < n; ++i) {
     add(this, xz[i], yz[i], data[i]);
   }
 
diff --git a/test/addAll-test.js b/test/addAll-test.js
index dd2f75e..23d312f 100644
--- a/test/addAll-test.js
+++ b/test/addAll-test.js
@@ -32,3 +32,13 @@ it("quadtree.addAll(data) computes the extent of the data before adding", () =>
   const q = quadtree().addAll([[0.4, 0.4], [0, 0], [0.9, 0.9]]);
   assert.deepStrictEqual(q.root(), [[{data: [0, 0]},,, {data: [0.4, 0.4]}],,, {data: [0.9, 0.9]}]);
 });
+
+it("quadtree.addAll(iterable) adds points from an iterable", () => {
+  const q = quadtree().addAll(new Set([[0.4, 0.4], [0, 0], [0.9, 0.9]]));
+  assert.deepStrictEqual(q.root(), [[{data: [0, 0]},,, {data: [0.4, 0.4]}],,, {data: [0.9, 0.9]}]);
+});
+
+it("quadtree(iterable) adds points from an iterable", () => {
+  const q = quadtree(new Set([[0.4, 0.4], [0, 0], [0.9, 0.9]]));
+  assert.deepStrictEqual(q.root(), [[{data: [0, 0]},,, {data: [0.4, 0.4]}],,, {data: [0.9, 0.9]}]);
+});