Remove lodash chunk, groupBy

(re: #6087)

modules/util/array.js

@@ -44,3 +44,48 @@ export function utilArrayUnion(a, b) {
 export function utilArrayUniq(a) {
     return Array.from(new Set(a));
 }
+
+// Splits array into chunks of given chunk size
+// var a = [1,2,3,4,5,6,7];
+// utilArrayChunk(a, 3);
+//   [[1,2,3],[4,5,6],[7]];
+export function utilArrayChunk(a, chunkSize) {
+    if (!chunkSize || chunkSize < 0) return [a.slice()];
+
+    var result = new Array(Math.ceil(a.length / chunkSize));
+    return Array.from(result, function(item, i) {
+        return a.slice(i * chunkSize, i * chunkSize + chunkSize);
+    });
+}
+
+
+// Groups the items of the Array according to the given key
+// `key` can be passed as a property or as a key function
+//
+// var pets = [
+//     { type: 'Dog', name: 'Spot' },
+//     { type: 'Cat', name: 'Tiger' },
+//     { type: 'Dog', name: 'Rover' },
+//     { type: 'Cat', name: 'Leo' }
+// ];
+//
+// utilArrayGroupBy(pets, 'type')
+//   {
+//     'Dog': [{type: 'Dog', name: 'Spot'}, {type: 'Dog', name: 'Rover'}],
+//     'Cat': [{type: 'Cat', name: 'Tiger'}, {type: 'Cat', name: 'Leo'}]
+//   }
+//
+// utilArrayGroupBy(pets, function(item) { return item.name.length; })
+//   {
+//     3: [{type: 'Cat', name: 'Leo'}],
+//     4: [{type: 'Dog', name: 'Spot'}],
+//     5: [{type: 'Cat', name: 'Tiger'}, {type: 'Dog', name: 'Rover'}]
+//   }
+export function utilArrayGroupBy(a, key) {
+    return a.reduce(function(acc, item) {
+        var group = (typeof key === 'function') ? key(item) : item[key];
+        (acc[group] = acc[group] || []).push(item);
+        return acc;
+    }, {});
+}
+