Functional Programming in JavaScript

Functional Programming in JavaScript

In this article, we will learn about declarative pattern, pure function, Immutability and side effects

In this article, we will learn about declarative pattern, pure function, Immutability and side effects.

What is Functional Programming

  • In computer science, functional programming is a programming paradigm or pattern (a style of building the structure and elements of computer programs)
  • Functional Programming treats computation as the evaluation of mathematical functions.
  • Functional Programming avoids changing-state and mutable data.

The above definition is taken from Wikipedia, now let’s try to understand the value and benefits of FP(functional programming) in this article.

Other Major programming paradigm or pattern

  • Procedural Programming
  • Object Oriented Programming
  • Meta Programming
  • Imperative Programming
  • Declarative Programming

Procedural Programming based upon the concept of the procedure call_, s_imply contain a series of computational steps to be carried out. Any given procedure might be called at any point during a program’s execution, including by other procedures or itself. Major procedural programming languages are COBOL, BASIC, C, ADA and GO

Object Oriented Programming based on the concept of objects, which contains data(attributes) and procedures(methods). This pattern is more closer to Functional Programming. Significant object-oriented languages include C++, Java, PHP, C#, Python, Ruby, Swift etc.

Meta Programming have the ability to treat programs as their data. It means that a program can be designed to read, generate, analyze or transform other programs, and even modify itself while running.

Imperative Pattern vs Declarative Pattern

  • Imperative Pattern focuses on describing how a program operates, it consists of commands for the computer to perform.
  • Declarative Pattern focuses on what the program should accomplish without specifying how the program should achieve the result.
  • Functional programming follows declarative pattern.
var books = [
  {name:'JavaScript', pages:450}, 
  {name:'Angular', pages:902},
  {name:'Node', pages:732}
];
/* Imperative Pattern */
for (var i = 0; i < books.length; i++) {
  books[i].lastRead =  new Date();
}
/* Declarative Pattern */
books.map((book)=> {
  book.lastReadBy = 'me';
  return book;
});
console.log(books);

  • In the above code snippet, we have added new attributes to each book(element) of books array and it has implemented in two different approaches.
  • First approach is with help of for loop, iterating over the array based on its length, then checking array index counter against array length and incrementing the index counter on each iteration. So, this is more like program/code is focusing or describing on how to operate for the desired output.
  • Second approach is with help of native JavaScript array method map() which takes function as argument and that function gets each element. So in this case code is not describing about how to operate but talking about what to accomplish and map() method behind the scene takes care of actual operation.

Mathematical Function or Pure Function

In mathematics, a function is a relation between a set of inputs and a set of permissible outputs with the property that each input combination is related to exactly one output.

In functional programming, these kinds of functions called pure function which only depends on the received input data to the function and does not alter the input data except the returned data.

Math.random() is not pure function because it always returns new value on each call.

Math.min(1,2) is an example of pure function which always returns same value with same set of inputs

Why Functional Programming

  • Its pure function, provides confidence of not changing things outside of its scope.
  • Its reduces the complexity, need not to worry about how it is doing it, focus will be only on what it is doing.
  • Ease of testing, because it does not depend on state of the application and result verification also will be easy.
  • It makes the code more readable.
  • Functional programming makes code easier to understand.

Examples of Functional Programming

Array Functions

In the above example, we are trying to filter only active meet-ups and we can see it can be achieved with two different approach. Here, second approach is Functional Programming where filter() method takes care of “how program operates” and program focuses only on input i.e. meetups array and care about output activeMeetupsFP but in first approach program cares about how to operate as well with for loop.

Similarly, below are other Array methods which help to achieve functional programming and reduce the complexity of the code.

  • find
  • map
  • reduce
  • every
  • some

Refer this github repo for the usage of above methods https://github.com/npatro/functional-programming/tree/master/code

Function Chaining

It’s a mechanism for invoking multiple method calls, each method returns an object, allowing the calls to be chained together in a single statement without requiring variables to store the intermediate results.

In the above code snippet, we want to print total members of all active meetups, considering 10% members might be duplicate.

Libraries to support FP

There are libraries which provide utility functions to make code more declarative.

  • RamdaJS
  • UnderscoreJS
  • lodash

Side Effects

Function or expression is said to have a side effect if it modifies some state of the program, which is outside of its own scope or has an observable interaction with its calling functions or the outside program besides returning a value.

let meetup = {name:'JS',isActive:true,members:49};
const scheduleMeetup = (date, place) => {
  meetup.date = date;
  meetup.place = place;
  if (meetup.members < 50)
    meetup.isActive = false;
}
const publishMeetup = () => {
  if (meetup.isActive) {
    meetup.publish = true;
  }
}
scheduleMeetup('today','Bnagalore');
publishMeetup();
console.log(meetup);

The program is having side effect because the actual responsibility of function scheduleMeetup is to add the dateand place of the meetup but it’s modifying the value of isActive as well on which some other functionpublishMeetup is depended upon and as a side effect the publishMeetup function will not have desired output because it’s input has changed in between. In the big program (real program), it’s really tough to debug the side effects.

Side effects are not always bad but we should be careful on when to have it.

Immutability

Immutability is important to make sure one function does not change the original data rather than should return new copy of the data after manipulation.

Like if Array and Objects are passing around multiple functions and we are not maintaining immutability then functions might not get the original copy of the array and object.

It is really hard to debug if something goes wrong in case of mutable object and array.

Mutability is not bad but it should be when to have it.

Immutable Libraries

JavaScript by-default does not provide anything to make the object and array Immutable. There are libraries which can help us to achieve the immutability.

  • Seamless-immutable
  • Immutable JS

Summary

The main aspects of Functional Programming is Pure and smaller Functions, Immutability and less Side Effects.

JavaScript Tutorial: if-else Statement in JavaScript

JavaScript Tutorial: if-else Statement in JavaScript

This JavaScript tutorial is a step by step guide on JavaScript If Else Statements. Learn how to use If Else in javascript and also JavaScript If Else Statements. if-else Statement in JavaScript. JavaScript's conditional statements: if; if-else; nested-if; if-else-if. These statements allow you to control the flow of your program's execution based upon conditions known only during run time.

Decision Making in programming is similar to decision making in real life. In programming also we face some situations where we want a certain block of code to be executed when some condition is fulfilled.
A programming language uses control statements to control the flow of execution of the program based on certain conditions. These are used to cause the flow of execution to advance and branch based on changes to the state of a program.

JavaScript’s conditional statements:

  • if
  • if-else
  • nested-if
  • if-else-if

These statements allow you to control the flow of your program’s execution based upon conditions known only during run time.

  • if: if statement is the most simple decision making statement. It is used to decide whether a certain statement or block of statements will be executed or not i.e if a certain condition is true then a block of statement is executed otherwise not.
    Syntax:
if(condition) 
{
   // Statements to execute if
   // condition is true
}

Here, condition after evaluation will be either true or false. if statement accepts boolean values – if the value is true then it will execute the block of statements under it.
If we do not provide the curly braces ‘{‘ and ‘}’ after if( condition ) then by default if statement will consider the immediate one statement to be inside its block. For example,

if(condition)
   statement1;
   statement2;

// Here if the condition is true, if block 
// will consider only statement1 to be inside 
// its block.

Flow chart:

Example:

<script type = "text/javaScript"> 

// JavaScript program to illustrate If statement 

var i = 10; 

if (i > 15) 
document.write("10 is less than 15"); 

// This statement will be executed 
// as if considers one statement by default 
document.write("I am Not in if"); 

< /script> 

Output:

I am Not in if
  • if-else: The if statement alone tells us that if a condition is true it will execute a block of statements and if the condition is false it won’t. But what if we want to do something else if the condition is false. Here comes the else statement. We can use the else statement with if statement to execute a block of code when the condition is false.
    Syntax:
if (condition)
{
    // Executes this block if
    // condition is true
}
else
{
    // Executes this block if
    // condition is false
}


Example:

<script type = "text/javaScript"> 

// JavaScript program to illustrate If-else statement 

var i = 10; 

if (i < 15) 
document.write("10 is less than 15"); 
else
document.write("I am Not in if"); 

< /script> 

Output:

i is smaller than 15
  • nested-if A nested if is an if statement that is the target of another if or else. Nested if statements means an if statement inside an if statement. Yes, JavaScript allows us to nest if statements within if statements. i.e, we can place an if statement inside another if statement.
    Syntax:
if (condition1) 
{
   // Executes when condition1 is true
   if (condition2) 
   {
      // Executes when condition2 is true
   }
}

Example:

<script type = "text/javaScript"> 

// JavaScript program to illustrate nested-if statement 

var i = 10; 

if (i == 10) { 

// First if statement 
if (i < 15) 
	document.write("i is smaller than 15"); 

// Nested - if statement 
// Will only be executed if statement above 
// it is true 
if (i < 12) 
	document.write("i is smaller than 12 too"); 
else
	document.write("i is greater than 15"); 
} 
< /script> 

Output:

i is smaller than 15
i is smaller than 12 too
  • if-else-if ladder Here, a user can decide among multiple options.The if statements are executed from the top down. As soon as one of the conditions controlling the if is true, the statement associated with that if is executed, and the rest of the ladder is bypassed. If none of the conditions is true, then the final else statement will be executed.
if (condition)
    statement;
else if (condition)
    statement;
.
.
else
    statement;


Example:

<script type = "text/javaScript"> 
// JavaScript program to illustrate nested-if statement 

var i = 20; 

if (i == 10) 
document.wrte("i is 10"); 
else if (i == 15) 
document.wrte("i is 15"); 
else if (i == 20) 
document.wrte("i is 20"); 
else
document.wrte("i is not present"); 
< /script> 

Output:

i is 20

How to Retrieve full Profile of LinkedIn User using Javascript

How to Retrieve full Profile of LinkedIn User using Javascript

I am trying to retrieve the full profile (especially job history and educational qualifications) of a linkedin user via the Javascript (Fetch LinkedIn Data Using JavaScript)

Here we are fetching LinkedIn data like Username, Email and other fields using JavaScript SDK.

Here we have 2 workarounds.

  1. Configuration of linkedIn developer api
  2. Javascript Code to fetch records

Configuration of linkedIn developer api

In order to fetch records, first we need to create developer api in linkedin which will act as token/identity while fetching data from other linkedin accounts.

So to create api, navigate to https://linkedin.com/developer/apps and click on 'Create Application'.

After navigating, fill in details like name, description and other required fields and then submit.

As we submit, it will create Client ID and Client Secret shown below, which we will be using in our code while communicating to fetch records from other LinkedIn account.

Note: We need to provide localhost Url here under Oauth 2.0. I am using my localhost, but you can probably use other production URLs under Oauth 2.0 where your app is configured. It will make your api  consider the Url as trusted which fetching records.

Javascript Code to fetch records

For getting user details like first name, last name,User image can be written as,

<script type="text/javascript" src="https://platform.linkedin.com/in.js">  
    api_key: XXXXXXX //Client ID  
    onLoad: OnLinkedInFrameworkLoad //Method that will be called on page load  
    authorize: true  
</script>  
<script type="text/javascript">  
    function OnLinkedInFrameworkLoad() {  
        IN.Event.on(IN, "auth", OnLinkedInAuth);  
    }  
  
    function OnLinkedInAuth() {  
        IN.API.Profile("me").result(ShowProfileData);  
    }  
  
    function ShowProfileData(profiles) {  
        var member = profiles.values[0];  
        var id = member.id;  
        var firstName = member.firstName;  
        var lastName = member.lastName;  
        var photo = member.pictureUrl;  
        var headline = member.headline;  
        //use information captured above  
        var stringToBind = "<p>First Name: " + firstName + " <p/><p> Last Name: " + lastName + "<p/><p>User ID: " + id + " and Head Line Provided: " + headline + "<p/>"  
        document.getElementById('profiles').innerHTML = stringToBind;  
    }  
</script>    

Kindly note we need to include 'https://platform.linkedin.com/in.js' as src under script type as it will act on this Javascript SDK provided by Linkedin.

In the same way we can also fetch records of any organization with the companyid as keyword.

<head>  
    <script type="text/javascript" src="https://platform.linkedin.com/in.js">  
        api_key: XXXXXXX ////Client ID  
        onLoad: onLinkedInLoad  
        authorize: true  
    </script>  
</head>  
  
<body>  
    <div id="displayUpdates"></div>  
    <script type="text/javascript">  
        function onLinkedInLoad() {  
            IN.Event.on(IN, "auth", onLinkedInAuth);  
            console.log("On auth");  
        }  
  
        function onLinkedInAuth() {  
            var cpnyID = XXXXX; //the Company ID for which we want updates  
            IN.API.Raw("/companies/" + cpnyID + "/updates?event-type=status-update&start=0&count=10&format=json").result(displayCompanyUpdates);  
            console.log("After auth");  
        }  
  
        function displayCompanyUpdates(result) {  
            var div = document.getElementById("displayUpdates");  
            var el = "<ul>";  
            var resValues = result.values;  
            for (var i in resValues) {  
                var share = resValues[i].updateContent.companyStatusUpdate.share;  
                var isContent = share.content;  
                var isTitled = isContent,  
                    isLinked = isContent,  
                    isDescription = isContent,  
                    isThumbnail = isContent,  
                    isComment = isContent;  
                if (isTitled) {  
                    var title = isContent.title;  
                } else {  
                    var title = "News headline";  
                }  
                var comment = share.comment;  
                if (isLinked) {  
                    var link = isContent.shortenedUrl;  
                } else {  
                    var link = "#";  
                }  
                if (isDescription) {  
                    var description = isContent.description;  
                } else {  
                    var description = "No description";  
                }  
                /* 
                if (isThumbnailz) { 
                var thumbnailUrl = isContent.thumbnailUrl; 
                } else { 
                var thumbnailUrl = "http://placehold.it/60x60"; 
                } 
                */  
                if (share) {  
                    var content = "<a target='_blank' href=" + link + ">" + comment + "</a><br>";  
                    //el += "<li><img src='" + thumbnailUrl + "' alt=''>" + content + "</li>";  
                    el += "<li><div>" + content + "</div></li>";  
                }  
                console.log(share);  
            }  
            el += "</ul>";  
            document.getElementById("displayUpdates").innerHTML = el;  
        }  
    </script>  
</body>  

We can get multiple metadata while fetching records for any any organization. We can get company updates as shown below.

Conclusion

We can also fetch any company specific data like company job updates/post, total likes, comments, and number of views along with a lot of metadata we can fetch which I have shown below.

Thank you for reading !

7 Best Javascript Iframe Libraries

7 Best Javascript Iframe Libraries

Iframes let you build user experiences into embeddable ‘cross-domain components’, which let users interact with other sites without being redirected. I have compiled 7 best Javascript iframe libraries.

Iframes let you build user experiences into embeddable ‘cross-domain components’, which let users interact with other sites without being redirected. I have compiled 7 best Javascript iframe libraries.

1. Zoid

A cross-domain component toolkit, supporting:

  • Render an iframe or popup on a different domain, and pass down props, including objects and functions
  • Call callbacks natively from the child window without worrying about post-messaging or cross-domain restrictions
  • Create and expose components to share functionality from your site to others!
  • Render your component directly as a React, Vue or Angular component!
    It's 'data-down, actions up' style components, but 100% cross-domain using iframes and popups!

Download


2. Postmate

Postmate is a promise-based API built on postMessage. It allows a parent page to speak with a child iFrame across origins with minimal effort.

Download


3. Iframe Resizer

Keep same and cross domain iFrames sized to their content with support for window/content resizing, in page links, nesting and multiple iFrames

Demo

Download


4. Iframely

Embed proxy. Supports over 1800 domains via custom parsers, oEmbed, Twitter Cards and Open Graph

Demo

Download


5. React Frame component

This component allows you to encapsulate your entire React application or per component in an iFrame.

Demo

Download


6. Seamless.js

A seamless iframe makes it so that visitors are unable to distinguish between content within the iframe and content beside the iframe. Seamless.js is a JavaScript library (with no dependencies) that makes working with iframes easy by doing all the seamless stuff for you automatically.

Demo

Download


7. Porthole

A proxy to safely communicate to cross-domain iframes in javascript

Demo

Download


Thank for read!