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2.4 KiB
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Use && for a More Concise Conditional |
Use && for a More Concise Conditional
The example given is
{condition && <p>markup</p>}
which is demonstrated below using the condition of the this.state.dinnerCooked boolean. If the boolean is true the markup included in the {} with the condition will display, if not it will not display
class MyComponent extends React.Component {
constructor(props) {
super(props);
this.state = {
dinnerCooked: true
}
}
render() {
return (
<div>
{this.state.dinnerCooked &&<h1>Dinner is Cooked!</h1>}//h1 tag contents will be displayed
</div>
);
}
};
## Hint:
You don't have to do a full ```if/then``` statement. Just write the condition you are checking.
## Solution:
As you can see, you don't have to write the full ```if/then``` statement. We only need to check the condition and see if it returns ```true``` or ```false```. In this case, we are checking the value of ```display```. If the value is ```true```, then you return the value to the right of ```&&```, which is ```<h1>Displayed!</h1>```. If the condition is ```false```, it returns nothing.
```jsx
class MyComponent extends React.Component {
constructor(props) {
super(props);
this.state = {
dinnerCooked: false
}
}
render() {
return (
<div>
{this.state.dinnerCooked &&<h1>Dinner is Cooked!</h1>}//h1 tag contents will NOT be displayed
display: true
}
this.toggleDisplay = this.toggleDisplay.bind(this);
}
toggleDisplay() {
this.setState({
display: !this.state.display
});
}
render() {
// change code below this line
return (
<div>
<button onClick={this.toggleDisplay}>Toggle Display</button>
{this.state.display && <h1>Displayed!</h1>}
</div>
);
}
};
Explanation from ReactJS.org documentation
You may embed any expressions in JSX by wrapping them in curly braces. This includes the JavaScript logical && operator. It can be handy for conditionally including an element
It works because in JavaScript, true && expression always evaluates to expression, and false && expression always evaluates to false.
Therefore, if the condition is true, the element right after && will appear in the output. If it is false, React will ignore and skip it.