Curious about how React handles rendering during a component's animation? Let's explore an example where a component is re-rendered due to a state change triggered during its animation.
Imagine a scenario where a component's animation lasts for 60 seconds, with a state change scheduled to occur after 30 seconds. The question arises: will React replace the physical DOM when the component is re-rendered mid-animation?
Here's my take on what might happen:
Step 1: Component Mounts Upon mounting, the component gets attached to the physical DOM. As the animation plays out and the timer for the state change ticks towards 30 seconds, React keeps track of the virtual DOM at the time of mounting.
Step 2: Triggering a State Change and Re-render When the state change kicks in after 30 seconds, causing the component to re-render, React compares the current virtual DOM with the previous one. Since the child component now has the "className-active" CSS class applied during the transition, React determines that an update is needed in the physical DOM (even if visually unnecessary), resulting in a screen flicker.
For a deeper dive into this scenario, here's a code snippet illustrating the process:
import React from 'react'
import CSSTransition from 'react-transition-group'
class ExampleComponent extends React.Component {
constructor(props) {
super(props);
this.state = {reRender : false};
setTimeout(() => {this.setState({reRender: true})}, 30000)
}
render() {
return (
<CSSTransition
appear={true}
in={true}
classNames='test'
timeout={60000}>
<span> test </span>
</CSSTransition>
)
}
}
And here are the relevant CSS classes used in the animation:
.test-appear, .test-enter{
opacity: 1;
}
.test-appear-active, .test-enter-active {
opacity: 0;
transition: opacity;
transition-duration: 60000;
}
.test-appear-done, .test-enter-done {
opacity: 0;
}
This setup begs the question: How does React handle state changes and maintain the virtual DOM during animations? Will it update the physical DOM precisely at the 30-second mark, or take into account the ongoing animation? Dive in to understand React's lifecycle intricacies!