React - Use State to Toggle an Element
Mastering React State: Toggling Elements with Confidence
React's state management system is a powerful tool for building dynamic and interactive user interfaces. One common use case involves toggling the visibility or behavior of elements based on user actions. This blog post dives into how to effectively leverage state to achieve element toggling in your React applications.
Toggling elements can introduce a subtle but important concept: handling asynchronous state updates. React might group multiple state updates together for efficiency, making it unreliable to directly access the previous state value within the update function itself.
To address this, we'll explore two approaches to ensure you're always working with the most recent state information:
1. Using a Function with setState
This approach is particularly useful when you need to access both the current state and props to determine the next state. Here's the breakdown:
this.setState((state, props) => ({
counter: state.counter + props.increment
}));
Inside the function passed to setState, you have access to the current state (state) and props (props). This allows you to perform calculations based on the latest values and return the new state object.
2. Using a Function Without Props
If you only need the current state to determine the next state, you can simplify the function further:
this.setState(state => ({
counter: state.counter + 1
}));
Here, the function receives just the current state (state) and returns the updated state object.
Key Takeaway
By embracing these techniques, you guarantee that your element toggling logic always operates on the most up-to-date state information, preventing unexpected behavior and ensuring a smooth user experience in your React applications.
Javascript
class MyComponent extends React.Component {
constructor(props) {
super(props);
this.state = {
visibility: false
};
// Change code below this line
this.toggleVisibility = this.toggleVisibility.bind(this);
// Change code above this line
}
// Change code below this line
toggleVisibility() {
this.setState(state => ({
visibility: !state.visibility
}));
}
// Change code above this line
render() {
if (this.state.visibility) {
return (
<div>
<button onClick={this.toggleVisibility}>Click Me</button>
<h1>Now you see me!</h1>
</div>
);
} else {
return (
<div>
<button onClick={this.toggleVisibility}>Click Me</button>
</div>
);
}
}
}View Statistics
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"Olivia, my eldest daughter, caught measles when she was seven years old. As the illness took its usual course I can remember reading to her often in bed and not feeling particularly alarmed about it. Then one morning, when she was well on the road to recovery, I was sitting on her bed showing her how to fashion little animals out of coloured pipe-cleaners, and when it came to her turn to make one herself, I noticed that her fingers and her mind were not working together and she couldn’t do anything. 'Are you feeling all right?' I asked her. 'I feel all sleepy,' she said. In an hour, she was unconscious. In twelve hours she was dead. The measles had turned into a terrible thing called measles encephalitis and there was nothing the doctors could do to save her. That was...in 1962, but even now, if a child with measles happens to develop the same deadly reaction from measles as Olivia did, there would still be nothing the doctors could do to help her. On the other hand, there is today something that parents can do to make sure that this sort of tragedy does not happen to a child of theirs. They can insist that their child is immunised against measles. ...I dedicated two of my books to Olivia, the first was ‘James and the Giant Peach’. That was when she was still alive. The second was ‘The BFG’, dedicated to her memory after she had died from measles. You will see her name at the beginning of each of these books. And I know how happy she would be if only she could know that her death had helped to save a good deal of illness and death among other children."
I just checked google books for BFG, and the dedication is there.
https://www.google.com.au/books/edition/_/quybcXrFhCIC?hl=en&gbpv=1
Roald Dahl, 1986
