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React Lessons from React School

There’s no way for a component to ask what key its parent specified. By default, all child components re-render automatically when the state of a parent component changes. This includes even the child components that weren’t affected by the change. Immutability makes it very cheap for components to compare whether their data has changed or not. You can learn more about how React chooses when to re-render a component in the memo API reference. React’s primary goal is to minimize the bugs that occur when developers are building UIs.

Just keep in mind that learning advanced React concepts doesn’t stop here. You can continue to learn about accessibility, test frameworks, and many more advanced concepts as needed. Anti-Patterns are the practices that you should avoid using in the ReactJS applications.

How to Create a List of Todo Elements

The lessons & challenges will guide you through these topics step by step while building the online supermarket shopping app. But, I told you that the thing which makes state the heart of your components is its mutable behaviour. Yes, now the point comes as to how we can change the state’s property. The answer is using ‘this.setState’ (please have a look at the above example).

React Lessons

If you want to use useState in a condition or a loop, extract a new component and put it there. You can find other built-in Hooks in the API reference. You can also write your own Hooks by combining the existing ones. All of these approaches also work for conditionally specifying attributes. If you’re unfamiliar with some of this JavaScript syntax, you can start by always using if…else.

React Components

You will now make two changes to the Game’s handlePlay function which is called when you click on a square. Lifting state into a parent component is common when React components are refactored. Currently, each Square component maintains a part of the game’s state.

  • The information you pass down like this is called props.
  • It doesn’t have a direct relationship with ReactJS.
  • You will rely on JavaScript features like for loop and the array map() function to render lists of components.
  • I advocate using functional components as it is more straightforward and require lesser coding.
  • So, you should know how to deploy the app and make it available for public access.
  • JSX is a syntax that looks like HTML but also has the power of JavaScript.

Now, we have a picture of how we can write components, but I have not told you how we can manage data in them. I think without data, components would be useless. So, we will have a look at how we can manage a component’s data (like fetching data from an API, React ‘state’ story, setting the state and so on). Use the component class when you need one of the things (lifecycle methods, state) and for presentation, use a functional component. As you might have seen in other React tutorials, they use class for creating their components. They put the logical as well as presentational parts in the same component which makes that component more complicated and bulky.

Data flow in a React application

They are used for presentation like how you want your component to look. So, we have to transpile it to JavaScript using JSX transformers (say babel) so that the browser can understand. By looking at the above example, you can understand what I was saying regarding code readability. I think this is enough on JSX and I hope now you are able to better understand the power of JSX in the React world. Once the calculation is done, the real DOM is updated with the things that are changed.

That code calls setCount(count + 1), incrementing the count state variable. The new count value is passed as a React Lessons prop to each button, so they all show the new value. By moving state up, you’ve shared it between components.

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