How to Avoid DOM Blocking in JavaScript

How to Avoid DOM Blocking in JavaScript

JavaScript programs run on a single thread in the browser and in runtimes such as Node.js. When code is executing in a browser tab, everything else stops: menu commands, downloads, rendering, DOM updates and even GIF animations.

JavaScript programs run on a single thread in the browser and in runtimes such as Node.js. When code is executing in a browser tab, everything else stops: menu commands, downloads, rendering, DOM updates and even GIF animations.

This is rarely evident to the user because processing occurs quickly in small chunks. For example: a button is clicked which raises an event that runs a function which makes a calculation and updates the DOM. Once complete, the browser is free to handle the next item on the processing queue.

JavaScript code can’t wait for something to occur; imagine the frustration if an app froze every time it made an Ajax request. JavaScript code therefore operates using events and callbacks: a browser or OS-level process is instructed to call a specific function when an operation has completed and the result is ready.

In the following example, a handler function is executed when a button click event occurs which animates an element by applying a CSS class. When that animation completes, an anonymous callback removes the class:

// raise an event when a button is clicked
document.getElementById('clickme').addEventListener('click', handleClick);

// handle button click event
function handleClick(e) {

  // get element to animate
  let sprite = document.getElementById('sprite');
  if (!sprite) return;

  // remove 'animate' class when animation ends
  sprite.addEventListener('animationend', () => {
    sprite.classList.remove('animate');
  });

  // add 'animate' class
  sprite.classList.add('animate');
}


ES2015 provided Promises and ES2017 introduced async/await to make coding easier, but callbacks are still used below the surface. For more information, refer to “Flow Control in Modern JS”.

Blocking Bandits

Unfortunately, some JavaScript operations will always be synchronous, including:

The following pen shows an invader which uses a combination of CSS animation to move and JavaScript to wave the limbs. The image on the right is a basic animated GIF. Hit the write button with the default 100,000 sessionStorage operations:

DOM updates are blocked during this operation. The invader will halt or stutter in most browsers. The animated GIF animation will pause in some. Slower devices may show a “script unresponsive” warning.

This is a convoluted example, but it demonstrates how front-end performance can be affected by basic operations.

Web Workers

One solution to long-running processes is web workers. These allow the main browser application to launch a background script and communicate using message events. For example:

// main.js
// are web workers supported?
if (!window.Worker) return;

// start web worker script
let myWorker = new Worker('myworker.js');

// message received from myWorker
myWorker.onmessage = e => {
  console.log('myworker sent:', e.data);
}

// send message to myWorker
myWorker.postMessage('hello');


The web worker script:

// myworker.js
// start when a message is received
onmessage = e => {
  console.log('myworker received:', e.data);
  // ... long-running process ...
  // post message back
  postMessage('result');
};


A worker can even spawn other workers to emulate complex, thread-like operations. However, workers are intentionally limited and a worker cannot directly access the DOM or localStorage (doing so would effectively make JavaScript multi-threaded and break browser stability.) All messages are therefore sent as strings, which permits JSON-encoded objects to be passed but not DOM nodes.

Workers can access some window properties, web sockets, and IndexDB — but they wouldn’t improve the example shown above. In most cases, workers are used for long-running calculations — such as ray tracing, image processing, bitcoin mining and so on.

(Node.js offers child processes which are similar to web workers but have options to run executables written in other languages.)

Hardware-accelerated Animations

Most modern browsers don’t block hardware-accelerated CSS animations which run within their own layer.

By default, the example above moves the invader by changing the left-margin. This and similar properties such as left and width cause the browser to reflow and repaint the whole document at every animation step.

Animation is more efficient when using the transform and/or opacity properties. These effectively place the element into a separate compositing layer so it can be animated in isolation by the GPU.

Click the hardware acceleration checkbox and the animation will immediately become smoother. Now attempt another sessionStorage write; the invader will continue to move even if the animated GIF stops. Note that the limb movement will still pause because that’s controlled by JavaScript.

In-memory Storage

Updating an object in memory is considerably faster than using a storage mechanism which writes to disk. Select the object storage type in the pen above and hit write. Results will vary, but it should be around 10x faster than an equivalent sessionStorage operation.

Memory is volatile: closing the tab or navigating away causes all data to be lost. A good compromise is to use in-memory objects for improved performance, then store data permanently at convenient moments — such as when the page is unloaded:

// get previously-saved data
var store = JSON.parse(localStorage.getItem('store'));

// initialise an empty store
if (!store || !store.initialized) {
  store = {
    initialized: true,
    username: 'anonymous'
    score: 0,
    best: { score: 1000, username: 'Alice' }
  }
};

// save to localStorage on page unload
window.addEventListener('unload', () => {
  localStorage.setItem('store', JSON.stringify(store));
});


Games or single-page applications may require more complex options. For example, data is saved when:

Web Performance

Web performance is a hot topic. Developers are less constrained by browser limits and users expect fast, OS-like application performance.

Do as little processing as infrequently as possible and the DOM will never be noticeably blocked. Fortunately, there are options in situations where long-running tasks can’t be avoided.

Users and clients may never notice your speed optimizations, but they’ll always complain when the application becomes slower!

Thanks for reading ❤

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!