How to Implement LINQ methods in JavaScript

2018-04-28

How to Implement LINQ methods in JavaScript - Part 8

blogentry, programming, quicktip, series

title: How to Implement LINQ methods in JavaScript - Part 8 date: "2018-04-28" banner: ./images/featured-image-2.jpg published_at: "2018-04-28T22:30:19.000Z" tags: "blogentry, programming, quicktip, series" author: Sung M. Kim

Photo by Pau Casals on Unsplash LINQ methods (All, Contains, SequenceEqual) in this article are somehow related in a way that they are predicates (returns true or false).

Here are the methods covered so far.

Part 1 〰️ Select, Aggregate, Where, OrderBy (Ascending, Descending)
Part 2 〰️ Any, Distinct, Concat, SelectMany
Part 3 〰️ Reverse, Zip, Min/Max
Part 4 〰️ Union, Intersect, Except
Part 5 〰️ Sum, Average, Count
Part 6 〰️ First, Last, DefaultIfEmpty, Skip, Take
Part 7 〰️ Empty, Repeat, Range
Part 8 〰️ All, Contains, SequenceEqual

🔴 Overview

In this article, I will cover following methods.

[table id=9 /]

The sample collections used in this part are shown as below.

C#

  
          private static List<Order> Orders = new List<Order>{
        
              new Order(id: 1, quantity: 40, orderDate: new DateTime(2018, 1,1,1,1,1,1)),
        
              new Order(id: 2, quantity: 20, orderDate: new DateTime(2018, 2,2,2,2,2,2)),
        
              new Order(id: 3, quantity: 30, orderDate: new DateTime(2018, 3,3,3,3,3,3)),
        
              new Order(id: 4, quantity: 10, orderDate: new DateTime(2018, 4,4,4,4,4,4)),
        
              new Order(id: 5, quantity: 20, orderDate: new DateTime(2018, 5,5,5,5,5,5)),
        
          };
        
          private static List<Order> DomesticOrders = new List<Order>{
        
              new Order(id: 1, quantity: 40, orderDate: new DateTime(2018, 1,1,1,1,1,1)),
        
              new Order(id: 11, quantity: 20, orderDate: new DateTime(2018, 11,2,2,2,2,2)),
        
              new Order(id: 111, quantity: 450, orderDate: new DateTime(2018, 11,1,2,2,2,2)),
        
              new Order(id: 1111, quantity: 230, orderDate: new DateTime(2018, 11,11,2,2,2,2)),
        
          };

view raw Blog Part 8.cs hosted with ❤ by GitHub

JavaScript

  
          const orders = [
        
            { id: 1, quantity: 40, orderDate: new Date(2018, 1, 1, 1, 1, 1) },
        
            { id: 2, quantity: 20, orderDate: new Date(2018, 2, 2, 2, 2, 2) },
        
            { id: 3, quantity: 30, orderDate: new Date(2018, 3, 3, 3, 3, 3) },
        
            { id: 4, quantity: 10, orderDate: new Date(2018, 4, 4, 4, 4, 4) },
        
            { id: 5, quantity: 20, orderDate: new Date(2018, 5, 5, 5, 5, 5) }
        
          ];
        
          const domesticOrders = [
        
            { id: 1, quantity: 40, orderDate: new Date(2018, 1, 1, 1, 1, 1) },
        
            { id: 11, quantity: 20, orderDate: new Date(2018, 11, 2, 2, 2, 2) },
        
            { id: 111, quantity: 450, orderDate: new Date(2018, 11, 1, 2, 2, 2) },
        
            { id: 1111, quantity: 230, orderDate: new Date(2018, 11, 11, 2, 2, 2) }
        
          ];

view raw Blog Part 8.js hosted with ❤ by GitHub

🔴 Examples

🔸 All

JavaScript has a method called Array#every, which works the same way as All does.

  
          private static void AllDemo(List<Order> orders)
        
          {
        
              var areAllOrdersPlacedOn2018 = orders.All(order => order.OrderDate.Year == 2018);
        
              WriteLine($"Are All Orders Placed On 2018?: {areAllOrdersPlacedOn2018}");
        
          }

view raw AllDemo.cs hosted with ❤ by GitHub

  
          function allDemo(orders) {
        
            const areAllOrdersPlacedOn2018 = orders.every(
        
              order => order.orderDate.getFullYear() === 2018
        
            );
        
            WriteLine(`Are All Orders Placed On 2018?: ${areAllOrdersPlacedOn2018}`);
        
          }

view raw allDemo.js hosted with ❤ by GitHub

Results

  
          // C#
        
          ====================  All DEMO - Check If All Orders Match a Condition  ====================
        
          Are All Orders Placed On 2018?: True
        
          // JS
        
          ====================  All DEMO - Check If All Orders Match a Condition  ====================
        
          Are All Orders Placed On 2018?: true

view raw All Demo Results hosted with ❤ by GitHub

every is more flexible as the callback is also passed an index.

🔸 Contains

There are so many ways implement contains but i used some as it short circuits (returns as soon as a condition is met).

  
          private static void ContainsDemo(List<Order> shippedOrders, List<Order> domesticOrders)
        
          {
        
              var firstDomesticOrder = domesticOrders.First();
        
              var containsDomesticOrder = shippedOrders.Contains(firstDomesticOrder, new OrderEqualityCompaprer());
        
              WriteLine($"Is the first domestic order shipped? {containsDomesticOrder}");
        
          }

view raw ContainsDemo.cs hosted with ❤ by GitHub

  
          function containsDemo(shippedOrders, domesticOrders) {
        
            const firstDomesticOrder = domesticOrders[0];
        
            const equalityComparer = order => order.id === firstDomesticOrder.id;
        
            const containsDomesticOrder = shippedOrders.some(equalityComparer);
        
            WriteLine(`Is the first domestic order shipped? ${containsDomesticOrder}`);
        
          }

view raw containsDemo.js hosted with ❤ by GitHub

Results

  
          // C#
        
          ====================  Contains DEMO - Do Shipped Orders Contain a Domestic Order?  ====================
        
          Is the first domestic order shipped? True
        
          // JS
        
          ====================  Contains DEMO - Do Shipped Orders Contain a Domestic Order?  ====================
        
          Is the first domestic order shipped? true

view raw Conains Demo Results hosted with ❤ by GitHub

OrderEqualityComparer object instance simply checks if two objects are the same by an ID. JavaScript version simply passes a callback which does the same.

🔸 SequenceEqual

You can use every here to check if two sequences are the same as every passes an index of current element to the callback.

  
          private static void SequenceEqualDemo(List<Order> shippedOrders, List<Order> domesticOrders)
        
          {
        
              var sameOrderAreSame = shippedOrders.SequenceEqual(shippedOrders);
        
              WriteLine($"Same Orders share the same sequence {sameOrderAreSame}");
        
              var areAllDomesticOrdersShipped = shippedOrders.SequenceEqual(domesticOrders);
        
              WriteLine($"Are All Domestic Order Shipped? {areAllDomesticOrdersShipped}");
        
          }

view raw SequenceEqualDemo.cs hosted with ❤ by GitHub

  
          function sequenceEqualDemo(shippedOrders, domesticOrders) {
        
            const sameOrderAreSame = shippedOrders.every(
        
              (order, i) => order.id === shippedOrders[i].id
        
            );
        
            WriteLine(`Same Orders share the same sequence ${sameOrderAreSame}`);
        
            const areAllDomesticOrdersShipped = shippedOrders.every(
        
              (order, i) => order.id === domesticOrders[i].id
        
            );
        
            WriteLine(`Are All Domestic Order Shipped? ${areAllDomesticOrdersShipped}`);
        
          }

view raw sequenceEqualDemo.js hosted with ❤ by GitHub

Results

  
          // C#
        
          ====================  SequenceEqual DEMO - Check If Two Sequences Are The Same  ====================
        
          Same Orders share the same sequence True
        
          Are All Domestic Order Shipped? False
        
          // JS
        
          ====================  SequenceEqual DEMO - Check If Two Sequences Are The Same  ====================
        
          Same Orders share the same sequence true
        
          Are All Domestic Order Shipped? false

view raw SequenceEqual Demo Results hosted with ❤ by GitHub

🔴 Closing Remark

I hope this article can serve as a cheat sheet (that's how I started this series).

Please let me know should you find any errors or improvements I can make to the codes. The full source code and instructions on how to run them are on GitHub.

	private static List<Order> Orders = new List<Order>{
	new Order(id: 1, quantity: 40, orderDate: new DateTime(2018, 1,1,1,1,1,1)),
	new Order(id: 2, quantity: 20, orderDate: new DateTime(2018, 2,2,2,2,2,2)),
	new Order(id: 3, quantity: 30, orderDate: new DateTime(2018, 3,3,3,3,3,3)),
	new Order(id: 4, quantity: 10, orderDate: new DateTime(2018, 4,4,4,4,4,4)),
	new Order(id: 5, quantity: 20, orderDate: new DateTime(2018, 5,5,5,5,5,5)),
	};

	private static List<Order> DomesticOrders = new List<Order>{
	new Order(id: 1, quantity: 40, orderDate: new DateTime(2018, 1,1,1,1,1,1)),
	new Order(id: 11, quantity: 20, orderDate: new DateTime(2018, 11,2,2,2,2,2)),
	new Order(id: 111, quantity: 450, orderDate: new DateTime(2018, 11,1,2,2,2,2)),
	new Order(id: 1111, quantity: 230, orderDate: new DateTime(2018, 11,11,2,2,2,2)),
	};

	const orders = [
	{ id: 1, quantity: 40, orderDate: new Date(2018, 1, 1, 1, 1, 1) },
	{ id: 2, quantity: 20, orderDate: new Date(2018, 2, 2, 2, 2, 2) },
	{ id: 3, quantity: 30, orderDate: new Date(2018, 3, 3, 3, 3, 3) },
	{ id: 4, quantity: 10, orderDate: new Date(2018, 4, 4, 4, 4, 4) },
	{ id: 5, quantity: 20, orderDate: new Date(2018, 5, 5, 5, 5, 5) }
	];

	const domesticOrders = [
	{ id: 1, quantity: 40, orderDate: new Date(2018, 1, 1, 1, 1, 1) },
	{ id: 11, quantity: 20, orderDate: new Date(2018, 11, 2, 2, 2, 2) },
	{ id: 111, quantity: 450, orderDate: new Date(2018, 11, 1, 2, 2, 2) },
	{ id: 1111, quantity: 230, orderDate: new Date(2018, 11, 11, 2, 2, 2) }
	];

	private static void AllDemo(List<Order> orders)
	{
	var areAllOrdersPlacedOn2018 = orders.All(order => order.OrderDate.Year == 2018);
	WriteLine($"Are All Orders Placed On 2018?: {areAllOrdersPlacedOn2018}");
	}

	function allDemo(orders) {
	const areAllOrdersPlacedOn2018 = orders.every(
	order => order.orderDate.getFullYear() === 2018
	);
	WriteLine(`Are All Orders Placed On 2018?: ${areAllOrdersPlacedOn2018}`);
	}

	// C#
	==================== All DEMO - Check If All Orders Match a Condition ====================
	Are All Orders Placed On 2018?: True

	// JS
	==================== All DEMO - Check If All Orders Match a Condition ====================
	Are All Orders Placed On 2018?: true

	private static void ContainsDemo(List<Order> shippedOrders, List<Order> domesticOrders)
	{
	var firstDomesticOrder = domesticOrders.First();
	var containsDomesticOrder = shippedOrders.Contains(firstDomesticOrder, new OrderEqualityCompaprer());
	WriteLine($"Is the first domestic order shipped? {containsDomesticOrder}");
	}

	function containsDemo(shippedOrders, domesticOrders) {
	const firstDomesticOrder = domesticOrders[0];
	const equalityComparer = order => order.id === firstDomesticOrder.id;
	const containsDomesticOrder = shippedOrders.some(equalityComparer);

	WriteLine(`Is the first domestic order shipped? ${containsDomesticOrder}`);
	}

	// C#
	==================== Contains DEMO - Do Shipped Orders Contain a Domestic Order? ====================
	Is the first domestic order shipped? True

	// JS
	==================== Contains DEMO - Do Shipped Orders Contain a Domestic Order? ====================
	Is the first domestic order shipped? true

	private static void SequenceEqualDemo(List<Order> shippedOrders, List<Order> domesticOrders)
	{
	var sameOrderAreSame = shippedOrders.SequenceEqual(shippedOrders);
	WriteLine($"Same Orders share the same sequence {sameOrderAreSame}");
	var areAllDomesticOrdersShipped = shippedOrders.SequenceEqual(domesticOrders);
	WriteLine($"Are All Domestic Order Shipped? {areAllDomesticOrdersShipped}");
	}

	function sequenceEqualDemo(shippedOrders, domesticOrders) {
	const sameOrderAreSame = shippedOrders.every(
	(order, i) => order.id === shippedOrders[i].id
	);
	WriteLine(`Same Orders share the same sequence ${sameOrderAreSame}`);

	const areAllDomesticOrdersShipped = shippedOrders.every(
	(order, i) => order.id === domesticOrders[i].id
	);
	WriteLine(`Are All Domestic Order Shipped? ${areAllDomesticOrdersShipped}`);
	}

	// C#
	==================== SequenceEqual DEMO - Check If Two Sequences Are The Same ====================
	Same Orders share the same sequence True
	Are All Domestic Order Shipped? False

	// JS
	==================== SequenceEqual DEMO - Check If Two Sequences Are The Same ====================
	Same Orders share the same sequence true
	Are All Domestic Order Shipped? false