Add max (#60)

index.d.ts

@@ -24,6 +24,8 @@ interface Array<T> {
     equalityComparer: IEqualityComparer<T>
   );
   Last<T>(): T;
+  Max<number>(): number;
+  Max<T>(xform: (x: T) => number): T;
   Prepend<T>(element: T): Array<T>;
   Reverse<T>(): Array<T>;
   Select<T, U>(xform: (x: T) => U): Array<U>;

index.js

@@ -7,6 +7,7 @@ const Empty = require('./src/Empty')
 const First = require('./src/First');
 const GroupJoin = require('./src/GroupJoin');
 const Last = require('./src/Last');
+const Max = require('./src/Max');
 const Prepend = require('./src/Prepend');
 const Reverse = require('./src/Reverse');
 const Select = require('./src/Select');
@@ -27,6 +28,7 @@ const bindAll = function() {
   Array.prototype.First = First;
   Array.prototype.GroupJoin = GroupJoin;
   Array.prototype.Last = Last;
+  Array.prototype.Max = Max;
   Array.prototype.Prepend = Prepend;
   Array.prototype.Reverse = Reverse;
   Array.prototype.Select = Select;
@@ -36,6 +38,7 @@ const bindAll = function() {
   Array.prototype.ToDictionary = ToDictionary;
   Array.prototype.Union = Union;
   Array.prototype.Where = Where;
+  Array.prototype.ElementAt = ElementAt;
 };
 
-module.exports = bindAll;
+module.exports = bindAll;

src/Max.js

@@ -0,0 +1,10 @@
+const _max = (a, b) => (a > b ? a : b);
+/**
+ * @template T
+ * @param {((x: T) => number)} xform
+ * @returns {T}
+ */
+function Max(xform = x => x) {
+  return this.reduce((a, b) => (xform(a) > xform(b) ? a : b));
+}
+module.exports = Max;

test/Max.spec.js

@@ -0,0 +1,21 @@
+const expect = require('chai').expect;
+require('..')();
+
+describe('Array#prototype#Max', function() {
+  const numInput = [1, 2, 3, 4, 5, 6];
+  it('Should return the max value in number array', function() {
+    const expected = 6;
+    const actual = numInput.Max();
+    expect(actual).to.eql(expected);
+  });
+  const objInput = [
+    { name: 'Bill', age: 32 },
+    { name: 'Jim', age: 13 },
+    { name: 'Bart', age: 25 }
+  ];
+  it('Should return the object with the max property in object array', function() {
+    const expected = { name: 'Bill', age: 32 };
+    const actual = objInput.Max(x => x.age);
+    expect(actual).to.eql(expected);
+  });
+});