100 lines
2.4 KiB
Markdown
100 lines
2.4 KiB
Markdown
---
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title: Alert
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tags: visual,beginner,state,effect
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---
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Creates an alert component with `type` prop.
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- Define appropriate CSS styles and animations for the component's elements.
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- Use the `React.setState()` hook to create the `isShown` and `isLeaving` state variables and set their values to `false`.
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- Define `timeoutId` to keep the timer instance for clearing on component unmount.
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- Use the `React.setEffect()` hook to update the value of `isShown` to `true` and clear interval by using `timeoutId` when component is unmounted.
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- Define `closeNotification` function to set the component is removed from DOM by displaying fading out animation and set `isShown` to `false` via `setTimeout()`.
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- Define the component, which renders the alert component with user defined `message` and a close button to remove the component from DOM.
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```css
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@keyframes leave {
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0% { opacity: 1 }
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100% { opacity: 0 }
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}
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.alert {
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padding: 0.75rem 0.5rem;
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margin-bottom: 0.5rem;
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text-align: left;
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padding-right: 40px;
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border-radius: 4px;
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font-size: 16px;
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position: relative;
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}
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.alert.warning{
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color: #856404;
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background-color: #fff3cd;
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border-color: #ffeeba;
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}
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.alert.error{
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color: #721c24;
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background-color: #f8d7da;
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border-color: #f5c6cb;
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}
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.alert.leaving{
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animation: leave 0.5s forwards;
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}
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.alert .close {
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position: absolute;
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top: 0;
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right: 0;
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padding: 0 0.75rem;
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color: #333;
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border: 0;
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height: 100%;
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cursor: pointer;
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background: none;
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font-weight: 600;
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font-size: 16px;
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}
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.alert .close:after{
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content: 'x';
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}
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```
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```jsx
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function Notification(props) {
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const [isShown, setIsShown] = React.useState(false);
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const [isLeaving, setIsLeaving] = React.useState(false);
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let timeoutId = null;
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React.useEffect(() => {
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setIsShown(true);
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return () => {
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clearTimeout(timeoutId);
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}
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}, [props.isShown, props.timeout, timeoutId]);
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const closeNotification = () => {
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setIsLeaving(true);
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timeoutId = setTimeout(() => {
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setIsLeaving(false);
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setIsShown(false);
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}, 250)
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}
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return isShown && (
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<div className={`alert ${props.type}${isLeaving ? ' leaving' : ''}`} role="alert">
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<button className="close" onClick={closeNotification} />
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{props.message}
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</div>
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)
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}
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```
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```jsx
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ReactDOM.render(<Notification type="info" message="This is info" />, document.getElementById('root'));
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```
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