Diving Deeper in JavaScripts Objects

Diving Deeper in JavaScripts Objects

JavaScript objects pack more things than their terse and concise syntax would naturally exhibit. Creating and using objects in JavaScript is so easy, effortless, and so flexible that a lot of developers never realize that there is more to it.

JavaScript objects pack more things than their terse and concise syntax would naturally exhibit. Creating and using objects in JavaScript is so easy, effortless, and so flexible that a lot of developers never realize that there is more to it.

We are going to uncover some of the hidden layers and understand the intricacies of JavaScript objects. After reading this article, you should be able to answer the following questions —

  • How to make a property undeletable?
  • What are accessor properties and what are their features?
  • How to make a property immutable or hidden?
  • Why some properties do not appear in for-in loops or Object.keys and some do?
  • How to “protect” objects from modification?
  • How to make sense of code such as
obj.id = 5;
console.log(obj.id)
// => '101' ( 5 in binary )

Types of Properties

Data Properties

You must have made countless objects like these

const obj = {
  name: 'Arfat',
  id: 5
}

obj.name 
// => 'Arfat'

In object obj, name and id properties are called Data Properties. These are the normal kind of properties that constitute most of the JavaScript code. What is, then, the other type of property?

Accessor Properties

They can also be understood as getters and setters of other languages such as C# or Python. An accessor property is a combination of two functions: the get and the set function.

Instead of using the traditional **key: value**syntax, we use the following syntax —

const accessorObj = {
  get name() {
    return 'Arfat';
  }
};

accessorObj.name;
// => 'Arfat'

const dataObj = {
  name: 'Arfat',
};

dataObj.name;
// => 'Arfat'

Look at accessorObj and compare it with dataObj. Right now, they exhibit the same behavior. We use the get keyword and follow it with a function declaration. Reading accessor properties do not need to use parentheses to invoke the function. That is, accessorObj.name**()**; is wrong.

When we access(read) accessorObj.name, the name function is executed and its return value becomes the final value of the name key.

The get function is called a getter since it is involved in getting the value of a key. If you update accessorObj.name = 'New Person’;, the update won’t happen. This is because we don’t have a corresponding setter function for the name key. Setter functions help in setting values of getter properties.

const accessorObj = {
  _name: 'Arfat',
  get name() {
    return this._name;
  },
  set name(value) {
    this._name = value;
  }
};

The setter function receives the assigned value as a parameter. Now, you can store the value in property or a global variable. In this case, we make a conventional “private” property _name and store the name value in it.

In the getter function, we can modify or override the property before returning its value. The following example should demonstrate this. It also answers one of the above questions.

const obj = {
  get name() {
    return this._name.toUpperCase();
  },
  set name(value) {
    this._name = value;
  },
  get id() {
    return this._id.toString(2); // Returns binary of a number
  },
  set id(value) {
    this._id = value;
  }
}

obj.name = 'Arfat';
obj.name;
// => 'ARFAT'

obj.id = 5;
obj.id;
// => '101

Why would anybody use accessor properties if normal data properties exist? There are often cases where you need to log the property access or maintain a history of all the values that the property has had. Accessor properties give us the full power of a function with the ease of use of object properties. You can read more about accessor usage here.

So how does JavaScript know which is an accessor property and which is a data property? Let’s find out.

Object Property Descriptors

At first glance, it might look like there is a one-to-one mapping between keys and values of an object. However, that’s not entirely true.

Property Attributes

Every key of an object contains a set of property attributes that define the characteristics of the value associated with the key. They can also be thought of as meta-data describing the key-value pair. In short, attributes are used to define and explain the state of object properties.

The set of property attributes is called the property descriptor.

In total, there are six property attributes. They are —

  • How to make a property undeletable?
  • What are accessor properties and what are their features?
  • How to make a property immutable or hidden?
  • Why some properties do not appear in for-in loops or Object.keys and some do?
  • How to “protect” objects from modification?
  • How to make sense of code such as

Why have we wrapped the attribute names in [[]]? Double square brackets mark internal properties used by the ECMA specifications. These are properties that JS programmer cannot touch directly from within the code. To manipulate internal properties, we’d need to use methods provided to us by the language.

Let’s see an example —

In the above image, the object has 2 keys: x and y. You can see the corresponding list of attributes associated with each property.

How can you get the same information in JavaScript? We can use the function Object.getOwnPropertyDescriptor to get that information. It takes an object and a property name and returns an object containing the required attributes. Here’s a code sample —

const object = {
  x: 5,
  y: 6
};

Object.getOwnPropertyDescriptor(object, 'x');

/* 
{ 
  value: 5, 
  writable: true, 
  enumerable: true, 
  configurable: true 
}
*/

Let’s see the attributes in more detail to know how they are helpful and then we’ll revisit the image.

[[Value]]

It stores the value retrieved by a get access of the property. Which means that when we do object.x in the above example, we actually retrieve its [[Value]] attribute. Any dot-access or square-bracket access of a Data property will work in this way.

[[Get]]

It stores the reference to the function that we declare while making a getter property. It is called with an empty arguments list to retrieve the property value each time a get access of the property is performed.

[[Set]]

It stores the reference to the function that we declare while making a setter property. It is called with an arguments list containing the assigned value as its sole argument each time a set access of the property is performed.

const obj = {
  set x(val) {
    console.log(val) 
    // => 23
  }
}

obj.x = 23;

In the above example, the right-hand-side of the assignment is passed as the val argument to a setter function. You can see this code for a demonstration.

[[Writable]]

This is a boolean value. It tells whether we can overwrite the value or not. If false, attempts to change the property’s value will not succeed.

[[Enumerable]]

This is also a boolean value. This attribute dictates whether the property is going to appear in for-in loops or not. If true, the for-in loop will be able to iterate on this property.

[[Configurable]]

This is a boolean too.

When it is false —

  • How to make a property undeletable?
  • What are accessor properties and what are their features?
  • How to make a property immutable or hidden?
  • Why some properties do not appear in for-in loops or Object.keys and some do?
  • How to “protect” objects from modification?
  • How to make sense of code such as

The effect of this property is also dependent on the property type. Apart from the above effects, it also does the following.

  • How to make a property undeletable?
  • What are accessor properties and what are their features?
  • How to make a property immutable or hidden?
  • Why some properties do not appear in for-in loops or Object.keys and some do?
  • How to “protect” objects from modification?
  • How to make sense of code such as

All six properties do not exist for each property type.

  • How to make a property undeletable?
  • What are accessor properties and what are their features?
  • How to make a property immutable or hidden?
  • Why some properties do not appear in for-in loops or Object.keys and some do?
  • How to “protect” objects from modification?
  • How to make sense of code such as

Working with Descriptors

Having learned about these descriptors, how can we set or update them on our own objects? There are a couple of functions in JavaScript that can be used to work with these descriptors. Let’s see them —

Object.getOwnPropertyDescriptor

We have seen this function above. It takes an existing object, and a property name. It returns either undefined or an object containing the descriptors.

Object.defineProperty

It’s a static method on Object that can define or modify a new property on a given object. It takes three arguments — the object, the property name, and descriptors. It returns the modified object. Let’s see an example —

const obj = {};

Object.defineProperty(obj, 'id', {
  value: 42
});

console.log(obj);
// => { }

console.log(obj.id);
// => 42

Object.defineProperty(obj, 'name', {
  value: 'Arfat',
  writable: false,
  enumerable: true,
  configurable: true
});

console.log(obj.name);
// => 'Arfat'

obj.name = 'Arfat Salman'

console.log(obj.name);
// => 'Arfat' 
// (instead of 'Arfat Salman')

Object.defineProperty(obj, 'lastName', {
  value: 'Salman',
  enumerable: false,
});

console.log(Object.keys(obj));
// => [ 'name' ]

delete obj.id;

console.log(obj.id);
// => 42

Object.defineProperties(obj, {
  property1: {
    value: 42,
    writable: true
  },
  property2: {}
});

console.log(obj.property1)
// => 42

It seems like a long example but it’s simple. Let’s go step by step —

  • How to make a property undeletable?
  • What are accessor properties and what are their features?
  • How to make a property immutable or hidden?
  • Why some properties do not appear in for-in loops or Object.keys and some do?
  • How to “protect” objects from modification?
  • How to make sense of code such as

Object.defineProperty sets one property at a time. There is a different variant of this function that can set multiple properties with their descriptors at the same time. It is aptly named Object.defineProperties](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperties) "https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperties)").

Protecting Objects

There are often cases where we don’t want anyone to tamper with our objects. Given the flexibility of JavaScript, it’s really easy to mistakenly re-assign properties of objects that we are not meant to touch. There are three major ways of protecting objects in JavaScript. Let’s look at them —

Object.preventExtensions

The Object.preventExtensions method prevents new properties from ever being added to an object (i.e. prevents future extensions to the object). It takes an object and makes it non-extensible.

Note that the properties can be deleted though.

const obj = {
  id: 42
};

Object.preventExtensions(obj);

obj.name = 'Arfat';

console.log(obj);
// => { id: 42 } 

You can check whether an object is non-extensible or not by using Object.isExtensible. If it returns true, you can add more properties to the object.

Object.seal

The seal method seals an object. It means —

  • How to make a property undeletable?
  • What are accessor properties and what are their features?
  • How to make a property immutable or hidden?
  • Why some properties do not appear in for-in loops or Object.keys and some do?
  • How to “protect” objects from modification?
  • How to make sense of code such as
const obj = {
  id: 42
};

Object.seal(obj);

delete obj.id 
// (does not work)

obj.name = 'Arfat';
// (does not work)

console.log(obj);
// => { id: 42 }

Object.isExtensible(obj);
// => false

Object.isSealed(obj);
//=> true

You can use Object.isSealed to test whether an object has been sealed or not.

Object.freeze

freeze is the maximum protection any object can have in JavaScript. It —

  • How to make a property undeletable?
  • What are accessor properties and what are their features?
  • How to make a property immutable or hidden?
  • Why some properties do not appear in for-in loops or Object.keys and some do?
  • How to “protect” objects from modification?
  • How to make sense of code such as
const obj = {
  id: 42
};

Object.freeze(obj);

delete obj.id 
// (does not work)

obj.name = 'Arfat';
// (does not work)

console.log(obj);
// // => { id: 42 }

Object.isExtensible(obj);
// // => false

Object.isSealed(obj);
// //=> true

Object.isFrozen(obj);
// => true

You can check whether an object is frozen or not using the Object.isFrozen function.

An important point to note is that these methods deal only with the direct properties of the objects. They do not modify nested objects.

Here’s a table summarizing the same.

The operations are in terms of properties. [CREATE] a new property, [READ] an existing property, [UPDATE] an existing property and [DELETE] an existing property.

Conclusion

Given how pervasive objects are on JavaScripts, it is important to understand the true power of objects. I hope the article was able to convey that effectively to you. I also hope that now you are able to answer the questions listed at the beginning of the article. Thanks for reading.

Learn More

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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!