ui/SectionList component (#4292)

* array chunking utility

* add SectionList component

* Add TODOs to indicate possible future work

* Add missing overlay style (as used in dapps at present)

js/src/util/array.js

@@ -0,0 +1,26 @@
+// Copyright 2015, 2016 Parity Technologies (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+// http://stackoverflow.com/questions/11318680/split-array-into-chunks-of-n-length
+export function chunkArray (array, size) {
+  return array
+    .map((item, index) => {
+      return index % size === 0
+        ? array.slice(index, index + size)
+        : null;
+    })
+    .filter((item) => item);
+}

js/src/util/array.spec.js

@@ -0,0 +1,29 @@
+// Copyright 2015, 2016 Parity Technologies (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+import { chunkArray } from './array';
+
+describe('util/array', () => {
+  describe('chunkArray', () => {
+    it('splits array into equal chunks', () => {
+      expect(chunkArray([1, 2, 3, 4], 2)).to.deep.equal([[1, 2], [3, 4]]);
+    });
+
+    it('splits array into equal chunks (non-divisible)', () => {
+      expect(chunkArray([1, 2, 3, 4], 3)).to.deep.equal([[1, 2, 3], [4]]);
+    });
+  });
+});