Components are a key part of React, a JavaScript library used to build user interfaces. They use to render, a core React function that transforms input data into HTML to display.
For example, a developer building an HTML interface can use the render function to add the sentence “Hello, world.” to a React component that, in turn, displays it inside a header or paragraph element.
That isn’t all React can do, however. After all, simply displaying text in HTML elements can be done with regular HTML. What makes React so useful is that it can also make changes to the user interface when things change.
How? To understand that, we need to understand state.
What is state?
State is an aspect of almost all programming languages. One way to think of state is as the program’s memory used to help it keep track of changes to data as it processes requests from the user.
Using variables to track state is an essential part of coding any kind of program, and with user interfaces, they are important for personalizing what the user sees. A program might track whether a user is a paid member or guest in a variable called MembershipType, for example, and grant access to different areas of the website, or simply change the look of the interface, depending on which is true.
The state of a variable can also change so that if a user starts as a guest but then becomes a member, the interface would know how to display the relevant parts of the interface each time.
How do stateful vs stateless components work?
All components in React work in essentially the same way. When coding the interface, developers insert a call to a specific component, which is similar to a function in many other programming languages. These components are what React uses to make on-the-fly changes to the interface.
Because they must be defined as functions, Stateless components are also called function components in the official React documentation. For this type of component, developers only need to pass one or more “props” (short for “properties”) to the component. The component will then read that property, apply it to the component as needed, and return the result to the body of the interface for display on the user’s screen.
In React, stateful components have to be defined as classes, rather than functions. The main other difference in using stateful components is that developers must also define the initial value of the state, which can then be modified by the program and add further nuance to the interface the user sees.
Who is React for exactly?
React is a popular JavaScript library that’s used to build interactive user interfaces.
React is very useful for interface developers and designers as a kind of shortcut. Everything it uses is also doable in JavaScript, but the creators of React have built a lot of functions and structures on top of standard JavaScript that make it significantly easier to create sophisticated interfaces.
Why is an understanding of stateful vs stateless components important?
The importance of stateful and stateless components lies chiefly in the fact that each has distinctly different use cases. Additionally, the amount of resources each uses is different.
It’s a bad idea to use entirely stateless components in React code because the interface will lack customizability and refinement. However, using entirely stateful components is an equally bad idea, because not all interface elements need the kind of functionality provided by React’s class-based state system.
In short, developers using React need to have a solid understanding of statefulness and how to use it in components to design effective interfaces.
What can you expect from using state in React?
When using stateful components in React, it’s important to remember that each component defines and manages its states separately.
State is initially defined within the class component by use of a this.state.variablename declaration that assigns a value to the variable. To change the value of a state, however, developers must use React’s setState method. That’s because attempting to redeclare the state using this.state.variablename will not refresh the component for the user.
In addition to understanding how to define and modify a state, developers must remember that it only exists within the specific component in which it is defined. State can be passed to child components, but if the stateful component is located inside of another component (called a parent) then that component will not be able to access its state values at all.
Use cases and examples of stateful vs stateless components in React.
The standard example of a stateful component used in the React documentation is the creation of a countdown timer. By setting a state that contains the value of seconds left and continually updating it with the setState method, developers can create a clock that works.
There are many other use cases for stateful components as well, such as returning comments on blog posts
Stateless components, on the other hand, are simple functions. They can’t do complex things, but they’re still very important in React as the bedrock on which an interface is built.
What are the benefits of state?
The main benefit of stateful React components is that they allow user interfaces to store data that can change over time. This provides a much more sophisticated experience to end-users, as developers can custom tailor the entire experience of their interfaces.
How do the two forms of state compare to one another?
It should be fairly clear by now that stateful components are a lot more complex than stateless components. They can access React methods, as well as store and modify data using state variables. Stateless components, on the other hand, only have access to basic output functionality and whatever variables are passed to them using Reacts “props” system.
Although in most cases the greater complexity of stateful components does not result in a significant reduction of performance, creating immense components with huge amounts of state variables and method calls can slow down an interface. A more effective programming habit is modularization or splitting code into multiple functions which then connect.
Summary
Put simply, if a React component is “stateful,” that means it has been defined as a class and can access methods, as well as being able to output dynamic, changing interface elements. If something is “stateless,” it is a simple piece of the interface that is unable to change based on user input or other changing data. Because both types of React components have benefits and drawbacks, understanding them is essential to coding effective, intuitive interfaces.
