Merge pull request #10570 from coveord/master

Add property `mapObject` on type `_ChainOfArrays<T>`

underscore/underscore-tests.ts

@@ -505,6 +505,12 @@ function chain_tests() {
 	var firstVal: number = _.chain([1, 2, 3])
 		.first()
 		.value();
+
+    let numberObjects = [{property: 'odd', value: 1}, {property: 'even', value: 2}, {property: 'even', value: 0}];
+    let evenAndOddGroupedNumbers = _.chain(numberObjects)
+        .groupBy('property')
+        .mapObject((objects: any) => _.pluck(objects, 'value'))
+        .value(); // { odd: [1], even: [0, 2] }
 }
 
 var obj: { [k: string] : number } = {

underscore/underscore.d.ts

@@ -5924,6 +5924,7 @@ interface _ChainSingle<T> {
 }
 interface _ChainOfArrays<T> extends _Chain<T[]> {
 	flatten(shallow?: boolean): _Chain<T>;
+	mapObject(fn: _.ListIterator<T, any>): _ChainOfArrays<T>;
 }
 
 declare var _: UnderscoreStatic;