Stacks vs. Queues In JavaScript

Stacks vs. Queues In JavaScript

Queues and stacks are two common data structures leveraged on technical interviews. Due to the fact that they’re quite similar in structure, they can be a bit confusing to differentiate. So today we’ll build a stack and a queue in JavaScript.

Queues and stacks are two common data structures leveraged on technical interviews. Due to the fact that they’re quite similar in structure, they can be a bit confusing to differentiate. So today we’ll build a stack and a queue in JavaScript.

Stacks

Stacks are data structures that follow the “last-in-first-out” or “LIFO” paradigm. We can think of them like a stack of books. In order to retrieve the third book in the stack, we have to take the fifth book off first, then the fourth book, until we retrieve the third book.

JavaScript doesn’t provide a native stack data structure, so we have to build our own with an array and a closure or a class.

Benefits

Stacks allow for constant-time adding and removing of an item. This is due to the fact that we don’t need to shift items around to add and remove them from the stack.

Constraints

Stacks, unfortunately, don’t offer constant-time access to the nth item in the stack, unlike an array. This means it can possible take O(n) where n is the number of elements in the stack, time to retrieve an item.

Methods

Stacks leverage the following methods:

  • pop(): Remove the top item from the stack
  • **push(item): **Add an item to the top of the stack
  • **peek(): **Return the item at the top of the stack
  • **isEmpty(): **Returns true if the stack is empty
Let’s Build

Let’s build a BookStack which will contain a stack of our favorite novels. What’s great about stacks is that the push and pop methods are the same name as the corresponding array methods we’ll use.

Constructor

We’ll define a class BookStack and give it a constructor method that has one property:

  • this.stack = [];
constructor() {
  this.stack = [];
}

Get

I’ll be adding a getter which returns the length of the stack. We’ll use this throughout our other methods.

get length() {
  return this.stack.length;
}

Push

We want to add the item to the end of the array, so we can use the array.push() method. The array.push() method returns the new length array.

push(item) {
  return this.stack.push(item);
}

Pop

We want to remove the last item in the array, so we can use the array.pop()method. The array.pop() method returns the item which was added, or undefined if the array is now empty.

pop() {
  return this.stack.pop();
}

Peek

We want to return, or peek at, the last item in the stack. Thus we just need to access the value at the last index.

peek() {
  return this.stack[this.length - 1];
}

isEmpty

We want to return true if there are no items in the stack. So if the length is zero, return true.

isEmpty() {
  return this.length === 0;
}

Putting It All Together

Our final BookStack code looks like this:

class BookStack {
  constructor() {
    this.stack = [];
  }
  
  push(item) {
    return this.stack.push(item);
  }
  
  pop() {
    return this.stack.pop();
  }
  
  peek() {
    return this.stack[this.length - 1];
  }
  
  get length() {
    return this.stack.length;
  }
  
  isEmpty() {
    return this.length === 0;
  }
}

You can also create this with a closure.

function BookStack() {
  const stack = [];
  
  return {
    push(item) {
	return stack.push(item);
    },

    pop() {
        return stack.pop();
    },

    peek() {
        return stack[this.length - 1];
    },

    get length() {
	return stack.length;
    },

    isEmpty() {
	return this.length === 0;
    }
  }
}

Let’s test it out with some book data.

let myBookStack = new BookStack();
myBookStack.push('Oathbringer');
myBookStack.push('The Stand');
console.log(myBookStack.length); // 2
console.log(myBookStack.peek()); // The Stand
myBookStack.pop();
console.log(myBookStack.length); // 1
console.log(myBookStack.peek()); // Oathbringer
console.log(myBookStack.isEmpty()); // false
myBookStack.pop();
console.log(myBookStack.isEmpty()); // true

You can view the CodePen here.

Queues

A queue is similar to a stack in structure and methods, however the paradigm is different. Queues use the “first-in-first-out” or “FIFO” method. This can be thought of like a queue, or line, of people waiting to buy movie tickets.

The person who’s been waiting the longest in line gets served before the person who just joined.

Use Cases

Queues are very similar to linked lists and are typically used in breadth-first searches or when implementing a cache.

Constraints

Queues are much harder to update when adding and removing nodes.

Methods

Queues leverage the following methods:

  • enqueue(item): Remove the top item from the stack
  • **dequeue(): **Add an item to the top of the stack
  • **peek(): **Return the item at the top of the stack
  • **isEmpty(): **Returns true if the stack is empty

Let’s Build

For this example, we’ll be using JavaScript classes. Please refer to the stack section if you’d like to see the function closure in action.

Constructor

We’ll define a class MovieQueue and give it a constructor method that has one property:

  • this.queue = [];
constructor() {
  this.queue = [];
}

Get

I’ll be adding a getter which returns the length of the queue. We’ll use this throughout our other methods.

get length() {
  return this.queue.length;
}

Enqueue

We want to add an item to the first index in an array (the back of the queue). So let’s use the array.unshift() method.

enqueue(item) {
  return queue.unshift(item);
}

Dequeue

We want to remove the first item in the queue, or the last item in the array. We can simply use the array.pop() method to do this.

dequeue() {
  return queue.pop();
}

Peek

We want to see what the first item in the queue is. Remember this is the last item in the array. We’ll use queue[this.length — 1] to grab this value.

peek() {
  return queue[this.length - 1];
}

isEmpty

We want to return true if the queue is empty. We can use the length method to grab this information.

isEmpty() {
  return this.length === 0;
}

Putting It All Together

Our final MovieQueue code looks like this:

class MovieQueue {
  constructor() {
    this.queue = [];
  }
  
  enqueue(item) {
    return this.queue.unshift(item);
  }
  
  dequeue() {
    return this.queue.pop();
  }
  
  peek() {
    return this.queue[this.length - 1];
  }
  
  get length() {
    return this.queue.length;
  }
  
  isEmpty() {
    return this.queue.length === 0;
  }
}


Let’s test it out with some names.

const myMovieQueue = new MovieQueue();
myMovieQueue.enqueue('Sandra');
myMovieQueue.enqueue('Rob');
myMovieQueue.enqueue('Lisa');
myMovieQueue.enqueue('Kai');
console.log(myMovieQueue.length); // 4
console.log(myMovieQueue.peek()); // Sandra
myMovieQueue.dequeue();
myMovieQueue.dequeue();
console.log(myMovieQueue.peek()); // Lisa

You can view the CodePen here.

I hope this tutorial gave you a better view on the differences between queues and stacks!

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!