How to use UNSAFE_componentWillMount() in React
The UNSAFE_componentWillMount() function was introduced in place of componentWillMount(), a life cycle method in React that was deprecated as of React 16.3.0. The prefix “UNSAFE_” was added to indicate that using this method could potentially lead to unsafe practices or cause issues in the future. This method handles the logic before a component is rendered. For instance, it was used to make API calls to some servers. It allows us to execute code synchronously as a component gets loaded or mounted to the DOM. This method is called during the mounting phase of the react life cycle.
Please make sure you are aware of React components and their life cycle.
The UNSAFE_componentWillMount() method is called when the component is loaded. It is triggered once throughout the component’s life cycle before its initial render. Once the component is initiated, the state value is overwritten by the updated value.
Syntax
UNSAFE_componentWillMount()() {// Perform the logic before rendering the component here}// Call the render method to display the HTML contents.render(){}
Before performing any activity, the component will first call the constructor and then the UNSAFE_componenetWillMount() method. Inside it, we can perform important actions to modify the state of the HTML before rendering it. Finally, the render() method is called, and all the changes made to the component are reflected in the rendered-out component.
Uses
There were quite a few uses for the UNSAFE_componentWillMount() hook.
It is most commonly used to display loaders before loading the component, making for a better user experience.
It is also used to set up the initial state of a component.
Fetching the data from servers is also one of its very important functions.
Event listeners can also be set up using the
UNSAFE_componentWillMount()method.
Code example
In the following example, we utilize the UNSAFE_componentWillMount() method to make an API call. Upon fetching the values, we employ it to set the state’s value, enabling us to later use this information in the render() method for displaying the fetched data.
import React from 'react';
import ReactDOM from 'react-dom';
import App from './app'; // Import your main App component or the root component of your application
import './index.css'; // Import any global styles
ReactDOM.createRoot(document.getElementById('root')).render(
<React.StrictMode>
<App />
</React.StrictMode>,
);Code explanation
Lines 3–10: In this part of the code the constructor method of the component is being declared. It’s used for initializing the component’s state. In this case, it sets the initial state with empty values for
mealandinstructions.Lines 12–20: We can see that in these lines of code
UNSAFE_componentWillMount()is being used to fetch data from the provided API endpoint and update the component’s state with the retrieved meal name and instructions.
Conclusion
In conclusion, UNSAFE_componentWillMount() is a life cycle method in React that is invoked just before a component is about to mount. It is a replacement for the componentWillMount() method which was historically used for tasks such as data fetching and state initialization, its use is discouraged in modern React applications due to potential side effects and inconsistencies.
