React Tutorial

React Tutorial

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1. Getting Started

The prompt provides a list of terms that are commonly used in React, a popular JavaScript library for building user interfaces. The terms include React, component, virtual DOM, JSX, constructor() method, render() method, state, setState() method, props, and binding methods. The prompt does not provide any additional context or information about these terms.

What is a Component?

State and setState()

Props (properties)

Binding Methods

2. Lifecycle Methods

Now that we have become familiar with most of the React basics and how components work and integrate into the development of a website. Since we know that React components are loaded onto the main page and then can be dynamically updated which means that they go through a certain cycle of stages that can be intervened in and the behavior can be updated. This cycle can be manipulated through what are called lifecycle functions at different stages. React class component lifecycle methods are used for a variety of purposes, including performing setup tasks when a component is first rendered, updating a component in response to changes in props or state, and cleaning up any resources that the component is using.

componentWillMount()

componentWillUnmount()

componentDidMount()

shouldComponentUpdate()

componentDidUpdate()

componentDidCatch()

Overview of Component Lifecycle

3. Functional Components and Hooks

Now that we have gone over the basics of class-based components, we will now explore a better and more concise way to write React components with functional components which are a lot more commonly used in React these days. Functional components are a way to define components in React that are simple, lightweight, and only consist of a render function. They are a great choice for simple, presentational components that only need to render some JSX and don't have their own state or lifecycle methods. In this section of the course, we'll look at how to use functional components with Hooks to manage state and other lifecycle events.

What is a Hook?

useMemo()

4. Advanced Topics

Now, we understand the basics of React with regards to the various kinds of components available and how to use them and exploit their lifecycle to our advantage in a webpage, we will now move on to some advanced topics. These topics will deal with topics like state management through Context API and the Consumer and Provider architecture in React and how these things make life easier in a production-level React App. Then we will move onto Routing in react and how it all works to produce a navigable React App without having to reload the page. This involves studying an important React package called “react-router-dom” which we will get into in this section.

React Router Dom

Conteúdo do Curso

React Tutorial

React Tutorial

useMemo()

useMemo is a hook in React that allows you to memorize a value. It is a way to optimize the performance of your application by avoiding unnecessary re-computations.

Here's an example of how to use useMemo:

In this example, the value of expensiveComputation is computed and cached using useMemo. The computation only happens if the count value changes. This can be a significant optimization if the computation is expensive, because it avoids re-computing the value on every render.

The first argument to useMemo is a function that returns the value you want to memoize. The second argument is the dependencies array, which works in the same way as the dependencies array in useEffect. If you pass an empty array ([]), the value will only be computed once, on the initial render. If you pass an array of values, the value will be re-computed anytime one of those values changes.

There are a few nuances to be aware of when using useMemo:

The value returned by the function passed to useMemo should be a primitive value, like a number or a string. It should not be an object or a function, because the reference to the object or function will change on every render, which will cause the value to be re-computed.
The function passed to useMemo should be pure, meaning it should not have any side effects and should always return the same value for the same input.
If you don't specify a dependencies array, the value will be re-computed on every render. This can be expensive and may cause performance issues, so it's important to be selective about which values you include in the dependencies array.

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Seção 3. Capítulo 5

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