feat(facade): add maximum method for ListWrapper

Author: btford

modules/angular2/src/facade/collection.dart

@@ -217,6 +217,27 @@ class ListWrapper {
  if (end == null) return len;
  return end < 0 ? max(len + end, 0) : min(end, len);
  }
+
+
+ static maximum(List l, fn(item)) {
+ if (l.length == 0) {
+ return null;
+ }
+ var solution = null;
+ var maxValue = double.NEGATIVE_INFINITY;
+ for (var index = 0; index < l.length; index++) {
+ var candidate = l[index];
+ if (candidate == null) {
+ continue;
+ }
+ var candidateValue = fn(candidate);
+ if (candidateValue > maxValue) {
+ solution = candidate;
+ maxValue = candidateValue;
+ }
+ }
+ return solution;
+ }
 }
 
 bool isListLikeIterable(obj) => obj is Iterable;

modules/angular2/src/facade/collection.ts

@@ -1,4 +1,4 @@
-import {isJsObject, global, isPresent, isArray} from 'angular2/src/facade/lang';
+import {isJsObject, global, isPresent, isBlank, isArray} from 'angular2/src/facade/lang';
 
 export var List = global.Array;
 export var Map = global.Map;
@@ -266,6 +266,26 @@ export class ListWrapper {
  }
  static toString<T>(l: List<T>): string { return l.toString(); }
  static toJSON<T>(l: List<T>): string { return JSON.stringify(l); }
+
+ static maximum<T>(list: List<T>, predicate: (T) => number): T {
+ if (list.length == 0) {
+ return null;
+ }
+ var solution = null;
+ var maxValue = -Infinity;
+ for (var index = 0; index < list.length; index++) {
+ var candidate = list[index];
+ if (isBlank(candidate)) {
+ continue;
+ }
+ var candidateValue = predicate(candidate);
+ if (candidateValue > maxValue) {
+ solution = candidate;
+ maxValue = candidateValue;
+ }
+ }
+ return solution;
+ }
 }
 
 export function isListLikeIterable(obj: any): boolean {

modules/angular2/test/facade/collection_spec.ts

@@ -76,6 +76,20 @@ export function main() {
  it('should respect the startIndex parameter',
  () => { expect(ListWrapper.indexOf(l, 1, 1)).toEqual(-1); });
  });
+
+ describe('maximum', () => {
+ it('should return the maximal element',
+ () => { expect(ListWrapper.maximum([1, 2, 3, 4], x => x)).toEqual(4); });
+
+ it('should ignore null values',
+ () => { expect(ListWrapper.maximum([null, 2, 3, null], x => x)).toEqual(3); });
+
+ it('should use the provided function to determine maximum',
+ () => { expect(ListWrapper.maximum([1, 2, 3, 4], x => -x)).toEqual(1); });
+
+ it('should return null for an empty list',
+ () => { expect(ListWrapper.maximum([], x => x)).toEqual(null); });
+ });
  });
 
  describe('StringMapWrapper', () => {