Hello Trailblazers,

Recently, I faced this issue in one of the projects I was working on. The issue was UNABLE_TO_LOCK_ROW, unable to obtain exclusive access to this record or N records, here N is just a placeholder in "N records" it can be 10, 20, 30 or even 100...200 for you. Let's have a look at the use case first and then we'll discuss the solution.

Use Case

Why it failed?

How to resolve it?

 Hello Trailblazers,

Welcome to the seventh tutorial in JavaScript Tutorial Series by SFDC Stop. In this tutorial, we're going to learn about Inheritance in JavaScript ES6. Inheritance is defined as the process where one (derived) class acquires the properties of another (base) class. We'll see how we can define a base class and a derived class, how we can call the constructor of the base class from the derived class, how we can use the base class methods from the derived class object with an example. This tutorial is published on SFDC Stop YouTube Channel. So, if you want to learn in detail, have a look at the tutorial video down below. Otherwise, you can scroll down to have a look at the code gist with explanation.

Tutorial Video

Concept

Code Gist with Explanation

We're going to define a simple class named as Phone. This will be our base class. Then we're going to define another class named as TouchPhone which will be our derived class. Let's have a quick look at the code below and then we'll understand it properly:

Let's talk about the base class first. Our Phone class is accepting two parameters in it's constructor namely: name and price. The name and price received in the constructor is assigned to the data members of the class with the same name i.e. name and price. After the constructor() we have two methods that are responsible to print the name and price of the phone namely: printName() and printPrice()

Now, let's talk about the derived class. Our TouchPhone classs is extending the Phone class using the extends keyword, this class is our derived class. Inside the TouchPhone class, we have a constructor which is accepting 3 parameters namely: name, price and touchSensitivity. The name and price received in the constructor are passed to the constructor of the base class by using the super().

We know that the base class Phone accepts two parameters inside the constructor i.e. name and price, therefore, we've passed name and price in our super(). After that we've assigned the 3rd parameter which is nothing but touchSensitivity to the data member of the derived class with the same name. After the constructor, we have defined one method named as printTouchSensitivity() which is responsible to print the touch sensitivity of the touch phone.

Conceptual Note: There are some properties which are common to every mobile phone for ex: name and price. That's why we've kept them as a part of the base (parent) class. Now, there can be some phone specific properties as well. Like: we can divide a phone into 2 basic categories:

1. A touch screen phone

2. A basic phone with keypad

For this, we have derived a class from the phone class and named it as TouchPhone, which represents a touch screen phone with an additional property i.e. touchSensitivity. As we're moving from parent to child class, we're also moving from Generalization to Specialization as the child class has more specific properties as compared to base class.

On line number 39, we have created an instance of our TouchPhone class named as iPhone and passed the name, price and sensitivity as iPhone11, 200 and 1.5 respectively to the derived class constructor. The name and price are automatically passed to the Phone class constructor through the super(). Then we're calling the printName(), printPrice() and printTouchSensitivity() methods from the derived class object. The concept to learn here is that: The derived class object can directly access the methods of the base class and can also access the constructor of the base class using the super().

After that we just added a console.log('---------') to divide the result into two parts. In the second part, we're creating an instance of the base class named as basicPhone. We're passing two values inside the constructor named as: Basic Phone and 100. Then we're printing the name and price of the basic phone by calling the printName() and printPrice() methods.

The output when the above code is executed is given below:

As you can see above, we're able to get the name, price and touch sensitivity of the touch phone as: iPhone11, 200 and 1.5 from the instance of the TouchPhone class. After that we're displaying the name and price of the basic phone which is Basic Phone and 100 using the instance of Phone class.

So, we understood that the derived class can easily call the member functions of the base class but is the reverse possible? Can the base class call the member functions of the derived class? Let's try that..!!

As you can see below, we modified our code a little and at the last line we're trying to call the printTouchSensitivity() method of the derived class from the instance of the base class. 

The execution of the above code resulted in an error as "Uncaught TypeError: basicPhone.printTouchSensitivity is not a function". This is because, we cannot call the member function of a derived class from the base class.

Hello Trailblazers,

Welcome to the sixth tutorial in JavaScript Tutorial Series by SFDC Stop. In this tutorial, we're going to learn about ES6 classes in JavaScript. We'll see how we used to define classes in JavaScript before ES6 and how easy it is to define a class now using ES6 syntax. We'll also learn about defining private variables in JavaScript classes. This tutorial is published on SFDC Stop YouTube Channel. So, if you want to learn in detail, have a look at the tutorial video down below. Otherwise, you can scroll down to have a look at the code gist with explanation.

Tutorial Video

Code Gist with Explanation

How we used to create a class in JavaScript before ES6?

We're going to define a simple class named as Car. The code for the class is given below:

As you can see above, the class car is defined as a function itself because classses in JavaScript are special functions. It will receive two parameters inside the constructor: name and speed, which are parameters to the car function in the code. These two parameters name and speed are used to initialize two data members of the class with the same name i.e. name and speed. Note that the data members are referred by using this keyword.

After the constructor, we have a function named as showSpeed() which is used to display the speed of the car. This function belongs to the Car class, that is why we've used Car.prototype.<function-name> syntax to define the member function. This function can access the data members of the car by using the this keyword.

After the function definition, we simply created the instance of the car class named as audi and passed the name and speed of the car in the constructor as: audi and 200. Finally, we called our showSpeed() method to display the speed of the car by using the class instance. The output when we run this code is given below:

The code is executed successfully and we're getting the expected result i.e. 200 which is the speed of the car.

How can we now define a class in JavaScript using ES6 syntax?

Using ES6 we can define a class using class keyword and the constructor of the class can be defined using constructor keyword. Let's have a look at the same Car class but this time, it's defined using ES6 as shown below:

As you can see in the above code, this time we've defined a Car class using the class keyword. This syntax is very similar to other programming languages. Inside the class, we've defined a constructor by using the constructor keyword. This constructor is accepting two parameters: name and speed. The two data members name and speed of the class are referred using this keyword inside the constructor and are given the values passed inside the constructor. After that we've a function inside the class itself named as showSpeed() which is responsible to display the speed of the car.

The remaining code snippet is same, we've again created the instance of the Car class named as audi and passed the name and speed of the car in the constructor as: audi and 300. Finally, we called our showSpeed() method to display the speed of the car by using the class instance. The output when we run this code is given below:

As you can see above, we're getting the speed of the car displayed as 300 in the console.

Can we have private variables inside classes in JavaScript?

The answer is YES! You can define private variables inside classes in JavaScript. Let's have a look at the modified code snippet to understand how:

As you can see above, we have added one more parameter to the constructor of our class Car named as: color. This parameter is assigned to a new data member identified by #color which is also declared above in the class. Here # specifies that, the color data member is private. Also note that it's mandatory to declare the private data member in the class body, that's why we've declared it above at line number 3.

We've also created one more member function named as showColor() which is displaying the value of color data member. Below the class, we've added two statements at line number 22 and 23, where we're displaying the name and speed of the car audi by directly accessing the data members outside the class. We can do that because the data members are public and we can access the public data members directly outside the class. However, we also have a commented statement at line 24 where we're trying to access the color data member outside the class.

As we know, that the color data member is private, we cannot access it outside the class. You can give it a try by un-commenting the line and running the code snippet. You'll get an error as shown below:

If we comment that line again and try to access the color using the showColor() function which is called at the last, the code will work fine and you'll get the output as shown below:

So, as you can see above, we're getting the value 300 from showSpeed(), then we're getting the name and speed of the car by directly accessing the public variables outside the class with values: audi and 300. Finally, we're displaying the color of the car by using the showColor() which is displayed as red as it's the same color that we've passed in the constructor of the class.

To summarize, the learnings are given below:-

• Before ES6, we used to define a class by using the syntax of a function because classes in JavaScript are Special Functions. The member functions of the class were defined outside the classs function.
• ES6 made it very simple to define a class using the class keyword. We can define a constructor inside the class as well by using the constructor keyword. The member functions of the class can be defined inside the class body itself.
• We can also define private variables in a class. Private variables must be explicitly declared inside the class body and are prefixed by a #. They can only be accessed inside class member functions.

That's all for this tutorial. I hope you liked it. All the code used in this tutorial is available on GitHub and you can have a look at that by clicking here. Make sure to have a look at the video if you want to learn in detail and let me know your feedback in the comments down below.

Happy Trailblazing..!!

 Hello Trailblazers,

Welcome to the fifth tutorial in JavaScript Tutorial Series by SFDC Stop. In this tutorial, we're going to learn about Spread Operator in ES6. We'll see how we can spread an array into multiple elements using the spread operator and also, how we can combine multiple elements into a single array by using spread operator as a rest parameter in ES6 JavaScript functions. This tutorial is published on SFDC Stop YouTube Channel. So, if you want to learn in detail, have a look at the tutorial video down below. Otherwise, you can scroll down to have a look at the code gist with explanation.

Tutorial Video

Code Gist with Explanation

How we used to pass array elements as parameters inside the function before ES6?

We're going to define a simple JavaScript function which will display the array elements passed as parameters. The code for that function is given below:

As you can see, we're having a function named as eats which has 3 parameters fruit1, fruit2, fruit3 and will print the statement consisting of the values of these. We're passing the fruits array elements into the function as fruits[0], fruits[1] and fruits[2]. The output when we run this code is given below:

How can we now pass array elements into function using spread operator in ES6?

ES6 has defined spread operator and it made it much simpler to pass array elements as parameters to a function in JavaScript. The updated code is given below:

As you can see in the above code, we're passing the array elements to function parameters by using the statement eats(...fruits);. When we specify three dots (...) before an array then it spreads the array into it's elements. That's why this operator is known as the spread operator. Therefore, while passing the array into the eats function, we're spreading it into multiple elements. The output when the above code is executed is given below:

As you can see above, the output is exactly the same as we've seen before.

What are Rest parameters in JavaScript ES6?

We've seen above that the ES6 spread operator (...) can be used to break an array into it's elements. But do you know that we can also use it to combine multiple JavaScript variables into a single array? We can pass multiple parameters to a JavaScript function and we can combine all those parameters to an array by using the spread operator. Let's see how:

As you can see above, we have created a function named as car. It has two parameters: name and features with a spread operator. This features parameter is nothing but an array and we're displaying the features of the car by iterating this array using the forEach loop. You can see above that we've called the car method with different values as: car('Audi', 'Great Speed', 'Good Color', 'Comfort', 'Good Looks');. So, here, the first argument is the car name Audi and is assigned to the name parameter. All the other arguments are car features and are combined together to form the features array by using the spread operator.

This is why we say that the spread operator can also be used as a Rest Parameter because it collects all the extra - rest of the parameters that are passed to a JavaScript function and forms an array. The output of the above code is given below:

As you can see above, all the features of the car are combined in a features array and we're able to display those features.

Concatenating two arrays using Spread Operator

Do you know we can also concatenate two arrays using spread operator? Let's have a look at the below code snippet to understand how:

As you can see in the above code snippet, we've created two arrays: features and moreFeatures. The features array is having 4 entries :- 'Great Speed', 'Good Color', 'Comfort' and 'Good Looks', whereas the moreFeatures array is having 2 entries:- 'Great Mileage' and 'Amazing Design'. We're using Array.push() method on the features array as features.push() which is basically used to push one element at the end of the array but here, we're spreading our moreFeatures array into multiple elements by using the spread operator. Therefore, these elements are then pushed one by one into the features array automatically and both the arrays are combined into the features array.

The output we're getting when the above code snippet is executed is given below:

As you can see above, it's pushing the elements of moreFeatures array into the features array using the push() and we're getting the output as 6, as the total number of elements are now 6. Also, we displayed the features array and it's showing us all the 6 features together. Therefore, we're able to concatenate two arrays using the spread operator. 

The same can be achieved when you're defining the second array as shown in the below code snippet:

As you can see above, we've passed the features array as an array element after the 'Amazing Design' entry while defining the moreFeatures array. We're spreading this array using the spread operator. This means that the moreFeatures array should contain all the elements of the features array after it's own two elements. Let's have a look at the output below as we're displaying the moreFeatures array using console.log() :

As you can see above, the moreFeatures array has all the elements of the features array appended after it's own elements, so, the spread operator is working perfectly fine.

To summarize, the learnings are given below:-

• Before ES6, if we need to pass array elements as parameters to js function, each array element was specified one by one using the index as array[0], array[1], array[2].
• ES6 made it very simple and we can simply pass the whole array as a single parameter by using the spread operator like: ...array
• In case, we're passing passing multiple values to a function we can combine them to an array using the spread operator. The spread operator is called a rest parameter in such a case.
• We can also concatenate two arrays using the spread operator.

That's all for this tutorial. I hope you liked it. All the code used in this tutorial is available on GitHub and you can have a look at that by clicking here. Make sure to have a look at the video if you want to learn in detail and let me know your feedback in the comments down below.

Happy Trailblazing..!!

Hello Trailblazers,

Welcome to the fourth tutorial in JavaScript Tutorial Series by SFDC Stop. In this tutorial, we're going to learn about ES6 Default Parameters in JavaScript Functions. We're going to see how we used to define default parameters before ES6 and how we can do it using ES6 syntax. This tutorial is published on SFDC Stop YouTube Channel. So, if you want to learn in detail, have a look at the tutorial video down below. Otherwise, you can scroll down to have a look at the code gist with explanation.

Tutorial Video

Code Gist with Explanation

We're going to define a simple JavaScript function which will add two values and display the result. The code for that function is given below:

Now, let's run this code once and then we'll learn about the default parameters. The output when we're calling this function with values 3 and 5 is given below:

How we used to define default parameters before ES6?

Now, let's see how we used to define default parameters before ES6. For this, we're going to provide a default value for the parameter b. The updated code is given below:

As you can see in the above code, inside the function we're checking that if b is defined i.e. we're passing a value for parameter b, we're using that b itself otherwise, we're going to assign a default value to b which is 2. The output when the above function is called is given below. This time, we're only going to pass 1 value to the function which will be used for parameter a and the parameter b will take up the default value.

As you can see above, we're passing only one parameter as 3 and the default value 2 is being taken up for parameter b giving us the total sum as 5.

How can we define default parameters using ES6 syntax?

ES6 has made it much simpler to define default parameters for functions in JavaScript. We're going to re-write the same function again now and see how we can define a default value for parameter b using ES6. The updated code is given below:

As you can see above, it is so simple to provide the default value for any parameter in ES6 by just giving that value with an equals = sign. Here we're giving the default value for parameter b as 2 by specifying b=2 in the function parameters itself. The output when the above function is called is given below:

As you can see above, we're getting the output as 5 when the parameters a and b are added as the default value for b is automatically considered as 2 and we're passing the value for a as 3.

How can we define a default value if we're passing an object to a function in JavaScript?

The syntax to define the default value, when an object is passed to a function parameter is given below:

As you can see in the above code snippet, we've defined a function named as personAge which is accepting two parameters, the age of the person and the person object itself. The person object has two properties:- firstName and lastName. We've defined the default value for firstName as Richard and the lastName as Hendricks. Therefore, if this function is called with just one parameter, these values will be taken up as the default values for the person object.

One important thing to notice is that we're assigning an empty object to the person object which has the default values like:- { firstName = 'Richard', lastName = 'Hendricks' } = {}. This is important because we're telling the JavaScript function that the default value for this second parameter as a whole is an empty object which has no values for firstName and lastName, so, the default values for these properties i.e. Richard and Hendricks can be taken up.

The output we're getting when the above function is called is given below:

As you can see above, we've only passed a single value for the age parameter as 20 and we're getting the output as: Richard Hendricks is 20 years old which is perfect. So, this is how you can define default values for an object passed as a parameter to a JavaScript function.

To summarize, the learnings are given below:-

• Before ES6, we were using conditional operator to define the default values for parameters
• ES6 made it very simple and we can simply define a default value for a parameter by providing the value after the = sign at the same place where the parameter is defined
• In case, we're passing an object to the function, we need to define a default value as an empty object after the = sign for the object parameter as a whole. Although, for the object properties, we can define the default values within the parameter definition. Both these steps are important to make sure that the object is initialized as well as the parameters also get their default values.

That's all for this tutorial. I hope you liked it. All the code used in this tutorial is available on GitHub and you can have a look at that by clicking here. Make sure to have a look at the video if you want to learn in detail and let me know your feedback in the comments down below.

Happy Trailblazing..!!

Hello Trailblazers,

In this post, I am going to discuss about one of my favorite updates from Salesforce Spring '21 Release (v51.0) for Salesforce Developers which is:

SOQL FIELDS() is Generally Available

Concept

Although most of the fields I queried are NULL :P because I just created some dummy account records using apex, but this is really amazing!!

What CAN be done and what NOT?

I even tried the above function by using Database.query() the file was saved successfully but I wasn't able to execute the function and got the same error as you can see below:

Although you can query all standard fields with some custom fields explicitly specified as shown below:

 Hello Trailblazers,

Welcome to the third tutorial in JavaScript Tutorial Series by SFDC Stop. In this tutorial, we're going to learn about ES6 Fat Arrow Functions in JavaScript. We're going to start from the beginning and see how we can define a function in JavaScript and finally we'll reduce that function to a single line of code using Fat Arrow sytnax. This tutorial is published on SFDC Stop YouTube Channel. So, if you want to learn in detail, have a look at the tutorial video down below. Otherwise, you can scroll down to have a look at the code gist with explanation.

Tutorial Video

Code Gist with Explanation

Q. Write a function to calculate the perimeter of a circle in JavaScript?

The basic syntax to define a function in JavaScript is given below where we're defining a function to calculate the perimeter of a circle.

As you can see in the above code, we have defined a function which is taking radius of a circle as a perimeter. Inside this function, we've a constant named as PI with value 3.14 and finally we're returning the perimeter of a circle which is nothing but 2 * PI * radius. Upon running the above code snippet which is calling the function with the value of radius as 10, the output we're getting is shown below:

As you can see above, we're getting the perimeter of the circle with radius 10 as 62.8. This is how you can Define a Simple Function in JavaScript. Now, let's update this code and this time we're going to assign a function to a variable and call a function afterwards. This is nothing but Another way of defining a function in JavaScript, as given below:

Here we're defining a function using the function keyword but instead of providing a name for the function after the function keyword, we're assigning that function to a variable with name perimeterOfACircle2 and using that variable to call this function in console.log statement. The output we're getting is shown below:

Here we've replaced function(radius) with (radius) => i.e. we're using the fat arrow symbol to point to the function body after the parameters are defined within paranthesis. According to this syntax, we keep the parameters before the fat arrow => and the body of the function after the fat arrow. The output we're getting when the above code is executed is given below:

As you can see above, the output is still the same. We've reduced the characters in our function code a little using the fat arrow syntax. Now, the question is:

CAN WE REDUCE THIS FUNCTION TO A SINGLE LINE WITH FAT ARROW SYNTAX?

The answer to this question is, YES! You can. Let's have a look at the updated code snippet below, where we've reduced this function code to a single line:

When you try to execute this code snippet, you'll get the output as shown below:

As you can see above, our output is still the same but we've reduced our JavaScript function to a single line using ES6 fat arrow syntax. Here are few things to notice in this code snippet:

1. Following the ES6 syntax we have to keep the parameters to the left hand side and the function body to the right hand side of the fat arrow =>
   
   
2. While reducing the function to a single line, you need to have the return value of the function to the right hand side of the fat arrow. Notice that here we've removed the constant PI but instead used the value 3.14 directly in the calculation followed by the fat arrow which will be returned. Also, we don't need to specify the return keyword here.
   
   
3. If you only have a single parameter passed inside your function, you don't need to cover it by paranthesis () you can simply keep it as is. You can see we've removed the paranthesis from the radius here.
   
   
4. Basically, we're reducing the function body to a single line which is being returned and specifying that line after the fat arrow.

Isn't it amazing..!! You can reduce your JS function to a single line using ES6 fat arrow syntax. Let's see an example function with multiple parameters as well. Have a look at the code below. This time we're going to calculate the perimeter of a rectangle by passing in two parameters length and breadth:

As you can see above, we've directly defined this function using ES6 syntax. this function is taking two parameters length, breadth and is returning the parameter of a rectangle which is nothing but 2 * (length + breadth).

The output of the function is given below:

As you can see above, after passing the length as 10 and breadth as 20 we're getting the parameter as 60 which is correct 2*(10+20). Here, we have multiple parameters therefore, covering them by paranthesis () is important to keep your code syntactically correct.

To summarize, the learnings are given below:-

• We can initialize a function by using the function keyword or by using the fat arrow =>
• While using a fat arrow, we need to keep the parameters to the left side of the fat arrow symbol => and the function body to the right side of the fat arrow symbol.
• If we can reduce the function body to one line, we can define it in a single line using fat arrow syntax by just keeping the return value after the fat arrow. In this case the return keyword is not mentioned.
  
• If we have a single parameter, we can remove the paranthesis () as well but we do need to specify the paranthesis otherwise.

That's all for this tutorial. I hope you liked it. All the code used in this tutorial is available on GitHub and you can have a look at that by clicking here. Make sure to have a look at the video if you want to learn in detail and let me know your feedback in the comments down below.

Happy Trailblazing..!!

Hello Trailblazers,

Welcome to the second tutorial in JavaScript Tutorial Series by SFDC Stop. In this tutorial, we're going to learn about constants in JavaScript. This tutorial is published on SFDC Stop YouTube Channel. So, if you want to learn in detail, have a look at the tutorial video down below. Otherwise, you can scroll down to have a look at the code gist with explanation.

Tutorial Video

Code Gist with Explanation

Let's have a look at the code snippet given below in which we're defining a constant named as MONUMENT with the value "Taj Mahal":

What do you think will be the output of above code snippet? When you try to execute this code, you'll get the output as shown below:

As you can see that the value Taj Mahal is displayed properly. This means that We can provide a value to a constant while defining it.

Now, let's break this constant definition into two statements as shown below:

What do you think will be the output of above code snippet this time? When you try to execute this code, you'll get the output as shown below:

Now, let's update this code snippet again and this time we'll initialize the MONUMENT constant and update it's value later on. The updated code snippet is given below:

What do you think the output will be when we execute the above code? When you try to execute this code, you'll get the output as shown below:

As you can see above, first of all, the value of the constant MONUMENT which was given during definition is displayed i.e. "Taj Mahal" but when we're trying to update the value of a constant we're getting an error as: Uncaught TypeError: Assignment to constant variable at <anonymous>:4:10. This means that We cannot assign a new value to a constant.

Now, let's consider one more scenario, this time, we're going to assign an object to a constant named USER. The code snippet for the same is given below:

When you try to execute this code snippet, you'll get the output as shown below:

As you can see above, the object which is assigned to our constant  USER is displayed properly. This object has two properties firstName and lastName. Now, let's update our code snippet and try to assign a new value to our USER constant. The updated code snippet is given below:

What will you think will happen now? The output of this code snippet is given below:

As you can see above, first of all our USER constant is displayed through first console.log statement with value of firstName as Rahul and lastName as Malhotra. After that we're getting an error which is similar to the error we saw previously i.e. Uncaught TypeError: Assignment to constant variable at <anonymous>:9:6

This means that even if you have provided an object to a constant you cannot update the constant as a whole. Now, one more question arises which is:

CAN WE UPDATE THE PROPERTY OF AN OBJECT ASSIGNED TO CONSTANT?

Let's find out. We've updated our code snippet again as shown below:

As you can see above, this time, we're not assigning a new value to our constant but we're updating the firstName to Richard and lastName to Hendricks. What do you think will happen now? Will JavaScript allow us to update the property of a constant or not? Let's see the output below:

As you can see, we haven't got any error. In the first console.log, an object is displayed with firstName as Rahul and the lastName as Malhotra and after updation, in the second console.log another object is displayed where the firstName is updated to Richard and the lastName is updated to Hendricks. Therefore, we got to know that If a constant is an object, we cannot assign a new value to that constant but we can update the properties of that constant.

To summarize, the learnings are given below:-

• We must initialize a constant while defining it
• We cannot assign a new value to a constant
• If the constant is an object, we can update the property of that constant

That's all for this tutorial. I hope you liked it. All the code used in this tutorial is available on GitHub and you can have a look at that by clicking here. Make sure to have a look at the video if you want to learn in detail and let me know your feedback in the comments down below.

Happy Trailblazing..!!

 Hello Trailblazers,

Welcome to the first tutorial in JavaScript Tutorial Series by SFDC Stop. In this tutorial, we're going to learn about the difference between let and var in JavaScript. This tutorial is published on SFDC Stop YouTube Channel. So, if you want to learn in detail, have a look at the tutorial video down below. Otherwise, you can scroll down to have a look at the code gist with explanation.

Tutorial Video

Code Gist with Explanation

Let's have a look at the code snippet given below:

What do you think will be the output of above code snippet? Think about it. When you try to execute this code, you'll get the output as shown below:

As you can see that the value is updated only inside the function, this means that the var keyword supports function scope as the value is updated only inside the function and the variable which is declared outside the function remains unchanged.

Now, let's replace this var keyword with let and check the output again. Below is our updated code:

What do you think will be the output of above code snippet this time? When you try to execute this code, you'll get the output as shown below:

 WHY SHOULD I USE LET INSTEAD OF VAR WHEN BOTH ARE SAME?

To answer this question, we need to study another code snippet. This time, we're going to replace the function with a block. Let's have a look at the code snippet given below:

What do you think the output will be when we execute the above code? When you try to execute this code, you'll get the output as shown below:

As you can see above, this time the value of the global variable is also updated even if we're assigning the value to a local variable inside an if block. This means that the var keyword doesn't support block scope. Let's try to replace this var keyword with let and check the output again. The updated code snippet is given below:

What do you think will be the output of the above code? When you try to execute this code snippet, you'll get the output as shown below:

As you can see above, this time the result is correct i.e. the value of the global variable is not updated inside the if block. This leads us to the conclusion that the let keyword supports block scope. 

To summarize, the learnings are given below:-

• Both var and let keyword supports function scope.
• var keyword doesn't support block scope
• let keyword supports block scope

This was the reason when let was introduced, it was said that let is the new var because is supports block scope which makes JavaScript more similar as different programming languages and it leads to less errors.

So, next time when you're about to declare a variable in your JavaScipt code, make sure to use let instead of var.

That's all for this tutorial. I hope you liked it. All the code used in this tutorial is available on GitHub and you can have a look at that by clicking here. Make sure to have a look at the video if you want to learn in detail and let me know your feedback in the comments down below.

Happy Trailblazing..!!

 Hello Trailblazers,

Welcome to the seventh and final tutorial in LWC Tutorial Series where we're building a ToDo App Project. We're focusing on the concept of Learning By Doing in this tutorial series. In this tutorial, we're going to refine our ToDo List component by adding a spinner and some validations in LWC. We're also going to deploy our todo list component to a Salesforce Org.

So, let's continue building the above application. This tutorial is published on SFDC Stop YouTube Channel. So, if you want to learn in detail, have a look at the tutorial video down below. Otherwise, you can scroll down to have a look at the code gist with explanation.

Tutorial Video

Code Gist with Explanation

Hello Trailblazers,

Welcome to the sixth tutorial in LWC Tutorial Series where we're building a ToDo App Project. We're focusing on the concept of Learning By Doing in this tutorial series. In this tutorial, we're going to learn how we can send the data to the apex controller from our ToDo List component by performing an imperative call to apex from LWC. We're going to use this while inserting a new task and deleting a task as we need to insert/delete the task record from Salesforce, when the button is clicked in our component.

So, let's continue building the above application. This tutorial is published on SFDC Stop YouTube Channel. So, if you want to learn in detail, have a look at the tutorial video down below. Otherwise, you can scroll down to have a look at the code gist with explanation.

Tutorial Video

Code Gist with Explanation

 Hello Trailblazers,

Welcome to the fifth tutorial in LWC Tutorial Series where we're building a ToDo App Project. We're focusing on the concept of Learning By Doing in this tutorial series. In this tutorial, we're going to learn how we can fetch the data from the apex controller for our ToDo List component using wire service in LWC. We're going to bind our wire service to a function in js which will receive the response. This time we'll be able to mutate the ToDoList as it won''t be directly binded with wire service. We'll also learn about RefreshApex function which will be used to refresh the browser cache.

So, let's continue building the above application. This tutorial is published on SFDC Stop YouTube Channel. So, if you want to learn in detail, have a look at the tutorial video down below. Otherwise, you can scroll down to have a look at the code gist with explanation.

Tutorial Video

Code Gist with Explanation