React is the most popular user interface library that is created based on javascript. In modern javascript, react manages a strong community because of ease of use and robustness. It is a suitable library for developing interactive UI that brings a smooth user experience.
Multiple components perform together to make a stunning react application. With simplicity and great exposure to javascript applications, react application development company wants to use function-based components. Hooks are exciting attributes in React version 16.8.
- Hooks allow the developer to use state and other functionality.
- The library comes with many built-in hooks to maintain states, develop references, isolate side effects, and enhance performance.
- UseEffect is an important hook in the library and works as part of the API.
- It helps developers to carry out side effects in functional components.
- Hook manages an ideal combination of react methods such as componentdDidUpdate, componentDidMount, and componentWillUnmount.
- It is a good choice for a developer to eliminate certain challenges caused by the life cycle method.
Implement Use Effect for Call Loading Function:
UseEffect hook works by default after every component render. Adding this hook in the component allows developers to run a callback as an effect. React will pass after performing or rendering DOM updates.
Whether you run callback only, the callback will pass after each render. Sometimes, developers pass the useEffect function after the first render as the second argument. In that scenario, they bring it as an empty array. The library will run a callback after the first render when running the second argument. Every time, elements in the array can change.
When passing the second argument as an empty array following each render, a library may evaluate the array and view nothing has changed. The callback will call after the initial render only. React hook makes a change in the passed-in function. The basic syntax of useEffect like
useEffect(() => {
console.log(“I Only run once (When the component gets mounted)”)
}, []);
Arguments Run to Hook:
Hook acquires two arguments: the first argument passed to useEffect is a function, and the second argument is an array of dependencies.
import { useEffect } from “react”;
import { render } from “react-dom”;
const App = (props) => {
useEffect(() => {
console.log(“Effect ran”);
}); //No second Argument
return <h1> KnowledgeHut By Upgrad! </h1>;
};
const root = document.getElementById(“root”);
render(<App />, root);
The function runs once following component mount for a pattern that validates react hook practice. On the other hand, it also contains huge hidden implementation details. A hook with a second array argument will focus on callback once mounting. It keeps value by different changes of an empty array.
The effect never accesses parameters, and react useEffect will callback either function or undefined. Whether hook function callback returns function acts as cleanup. Cleanup can pass before the effect reaches.
If you control what effect passes after the component mounts, passing an array of dependencies as the second argument is the best option. Dependency is similar to the value defined outside the hook. React compares the present value to the previous one. If it does not equal, the effect can be called. You can call an argument if needed.
If it is absent, the effect will pass after each render. Developers run empty arrays if they need the effect to pass on the initial render. Props and states are dependencies. Values define inside the component, and the outside hook must pass as a dependency.
Use Function as a Dependency:
If you use a function outside hook and call them inside effect, you should pass it as a dependency.
function App(){
const [data, setData] = useState(null);
const fetchData = () => {
// some code
}
useEffect(() => {
fetchData(); //used inside useEffect
}, [fetchData])
It is not suitable to define the function outside and call them inside effects. Passed dependency is a function that serves as an object. FetchData can call on every render. Library evaluates FetchData from previous and current render. If both of them are not the same, the call will trigger.
Usage of UseEffect:
React useEffect removes every single lifecycle function that you run. The callback function run to hook will pass side effects. React passes them on every component rendered by default. Side effects are expensive and performance-intensive to pass on every render. With the help of Hook, developers gain complete control and use dependency array arguments that pass to Hook.
Side Effect Work After Every Render:
It is the default case. Whether you never run a dependency array to hook, the callback function performs on every render.
Side Effect Passes Only One After The First Render:
You can run the side effect after the initial render once. In that case, data will be fetched by making an API call and storing the response in the state variable after the first render.
Side Effect Passes After State Value Changes:
You may run side effects based on state value. You should run a state variable to hook as a dependency array to resolve certain use cases.
The hook is ideal for fetching data, manually adjusting DOM in react components, and setting subscriptions. Side effects are an operation that completes before in the component.
UseEffect Code:
React has several functional components. Hooks are important things in the library to maintain special events. UseEffect will pass when the component renders every time. When it comes to component initialization, you may also execute code at initial rendering.
The array is the second parameter when you classify states and props effects. Whether the array is empty, react executes code one at first rendering. Code focuses on the variable value that counts at different times. The hook will accomplish this by considering changes with a variable value. React component pays attention to the hook only once.
Conclusion:
A proper understanding of best practices and design concepts of useeffect is essential. When you can load functions with this hook, you can access great support from the React company and create a project. So, you must carefully understand the above details and realize the usage of the hook in the project. Please go through this link If you want to know more about Ways to Set Focus on an Input Field After Rendering in React.
