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    React Functional Component: Uses with Examples

    Introduction About React Functional Component:

    React Functional Component are currently the present required components that are written in modern React applications. Although, in the past, there have already been various React component Types. But when the React Hooks were introduced then it became possible to write our entire application only with just functions considering them as React components.  

    Here we’ll provide you an in-depth guide about Functional Components of React which are actually JavaScript functions acting as React components. This in return gives JSX (React’s Syntax) in order to prepare you well after you read this article so that you can implement modern React applications with them. 

    Functional components in React are actually a way that makes your React code easier to test as well as achieve better performance. Functional components in React are the easiest way to achieve them all! However the prerequisites for this is that you just require to have a basic understanding of React, however, the prior knowledge of ES6 will also come in handy. 

    So far, we have been writing our components with the help of the class syntax along with the render method. Using this method many of our components can be created. Although, we do have a smaller and even more compact way of creating components that have only got a render method.  This came to be known as functional components. It is safe to say that the functional components have not got any state. They are just some simple functions that return as to what should be displayed on the screen. The first parameters passed into the functions are actually the props passed to the components.

    Here’s an example to demonstrate the same:

    As we all can see here we are exporting a function that takes in an object which is actually the props passed to the component.  Here we destroyed the props in order to pull out the days and onDayClicked props. After that, we have returned the exact same thing that we had in our render function as before. We got to agree that the code became much smaller and simpler to understand. Even the React team also recommends this method to write components whenever you can.

    Many React developers also think that the functional components are going to be one of the things that the React team will definitely work on optimizing it in the future when the other newer versions of Reacts will be released.

    So, it’s recommended to use Functional components whenever you can in your application’s codes. However, this is not the only way where the components can be refactored in this manner. 

    What do we mean by React Functional Component?

    There exists two main types of components in React:

    • Functional components
    • Class components 

     

    The difference between both of them is pretty in a literal way. Function components are basically functions and Class components are EcmaScript6 classes. The only requirement for a functional component is to accept props as an argument and finally return valid JSX. Consider the following:

    And there we have our functional component! The lack of state and lifecycle methods is the major thing that makes these types of components different from those of class components. This is also the reason why functional components are often referred to as Stateless components. Now, if we have to write  the same component in EcmaScript6, we will write it as follows:

    If you have never come across ES6 before then this might look absurd to you. We will now see how to write it as a class component:

    We can see that the above code snippet just contradicted the most basic rule i.e. if we have got a class component that has got only one render method then it should always be made as a functional component.  

    Why Should We Use React Functional Components?

    You might wonder why there is all a fuss about a component that actually removes the functionality. Contrary to that it turns out that constraints are very important. The following 6 reasons can tell you why to use functional components:

    • Function of components are simple to reason about
    • Functional components are easy to test
    • The functional components have the potential to give a better performance
    • Function of components are very easy to debug
    • Functional components can be reused again and again
    • Function of components are capable of reducing coupling

     

    Why Should We Not Use Functional Components?

    If we consider the functional components as a hammer, then it is important to understand that not every problem is a nail. Not every React problem can be solved using the Function of components. There is a reason why React has also included the class components. 

    The general preliminary trial that can be used is to always start with the functional component. It is extremely trivial of you to refactor to a class component if you find out that there is a need for lifecycle methods or it is just better to have a small segment of the component-level state. However, all world-renowned companies like Facebook, Airbnb, Netflix are readily using functional components in React because it’s pretty evident that the pros of using it definitely outweigh the cons.

    React Functional Components:

     

    Props:

    In this, we will be learning about React functional components with props. In React, props are used for passing information from one component to another. If one doesn’t know about the props in React, one point that is very important to keep in mind is that props in React are always passed down the component tree. The props are the parameters for React Functional Components but the components that we use can stay generic for us to run react functional components. We can decide from the outside what we are trying to render and when rendering a component, we can pass the props as HTML attributes for the component while we run react functional components.

    In the functional component, the props object is made available as an argument in the signature of the function. Since the props are always counted as objects, and very often we need to extract the information from the props anyway so the JavaScript object destructing comes very handy in this situation.

     

    Arrow Function Component:

    As we were introduced to JavaScript ES6, various new coding concepts were introduced to JavaScript and therefore also to React. One example of that would be how JavaScript functions can be expressed as the lambda, also known as the arrow function. This is the reason why a Function component might also be called the Arrow Functional Component or even the Lambda Functional Component. Let us take a look at the refactored React Component with an Arrow Function: 

    Both of the Arrow Function Components that are present in React makes use of a function block body nowadays. But we can make the second component more lightweight with a very concise body. What it does is that it returns the output of the component without having to do anything else in between. When we leave out the curly braces, what happens is, the explicit return becomes implicit and that can be left out as well. 

    When we are using the arrow components when we run react functional components, there is no change in the props.

     

    Stateless Functional component:

    All the components that we saw this far, can be called Stateless functional components. What they do is receive the input signals as props and return the output as jsx. If there is any input that is available from the props, then it helps in shaping the output that is rendered. These types of functional components have no side effects as they do not manage state so they can not access the local storage of the browser. They are called functional Stateless components because as their name suggests, they are stateless and can be expressed by a function. However, if we want to function in the state components, then we have react hooks to make even that possible. 

     

    State:

    What makes it possible for use to use state is react Hooks in any Functional Components. It might be possible to move all components logic to our other function and not pass any props to it. State is what helps us in making React Components more interesting:

    Conclusion:

    Since we were introduced with React Hooks in React, the React Functional Component are no longer behind the Class Components. If we look at them feature-wise. We can have state, lifecycle, and even side-effects in React’s Functional Components. This is why it is very strongly believed that React is planning to move even more towards the functional components. It is very much light in weight as compared to the Class Components. It even offer us a very sophisticated API for reusable and yet very encapsulated logic with the help of React Hooks. In this article, we have presented you with almost everything that you must know while starting with React Functional Components. 

     

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