One way of animating a component is to attach a `CSS class` to it. But, when animation is done, you have to detach the `CSS class` so that you can re-attach when you want to animate again.
Here is a basic example:
<!-- begin snippet: js hide: false console: true babel: true -->
<!-- language: lang-js -->
class App extends React.Component {
constructor(props) {
super(props);
this.state = {
animateFlag: false
};
}
componentDidUpdate() {
if (this.state.animateFlag) {
setTimeout(() => {
this.setState({ animateFlag: false });
}, 3000);
}
}
render() {
return (
<div className="App">
<button
onClick={() =>
this.setState({ animateFlag: !this.state.animateFlag })
}
>
{this.state.animateFlag ? "Wait" : "Re-animate"}
</button>
<div className={this.state.animateFlag ? "text animate" : "text"}>
Hello CodeSandbox
</div>
</div>
);
}
}
const rootElement = document.getElementById("root");
ReactDOM.render(<App />, rootElement);
<!-- language: lang-css -->
.text {
font-size: 40px;
}
.text.animate {
animation: formFading 3s;
}
@keyframes formFading {
0% {
opacity: 0;
}
100% {
opacity: 1;
}
}
<!-- language: lang-html -->
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script>
<div id="root"></div>
<!-- end snippet -->
Note that, I am setting `animateFlag` to `false` in `ComponentDidUpdate`, so that when I click the `Re-animate button` again, I can re-attach the `animate` class to the `div` element.
I set timeout duration to 3000ms because, the animation takes 3000ms.
That's *property spread notation*. It was added in ES2018, but long-supported in React projects via transpilation (as "JSX spread attributes" even though you could do it elsewhere, too, not just attributes).
`{...this.props}` *spreads out* the "own" properties in `props` as discrete properties on the `Modal` element you're creating. For instance, if `this.props` contained `a: 1` and `b: 2`, then
<Modal {...this.props} title='Modal heading' animation={false}>
would be the same as
<Modal a={this.props.a} b={this.props.b} title='Modal heading' animation={false}>
But it's dynamic, so whatever "own" properties are in `props` are included.
Since `children` is an "own" property in `props`, spread will include it. So if the component where this appears had child elements, they'll be passed on to `Modal`. Putting child elements between the opening tag and closing tags is just syntactic sugar — the good kind — for putting a `children` property in the opening tag. Example:
<!-- begin snippet: js hide: true console: true babel: true -->
<!-- language: lang-js -->
class Example extends React.Component {
render() {
const { className, children } = this.props;
return (
<div className={className}>
{children}
</div>
);
}
}
ReactDOM.render(
[
<Example className="first">
<span>Child in first</span>
</Example>,
<Example className="second" children={<span>Child in second</span>} />
],
document.getElementById("root")
);
<!-- language: lang-css -->
.first {
color: green;
}
.second {
color: blue;
}
<!-- language: lang-html -->
<div id="root"></div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script>
<!-- end snippet -->
Spread notation is handy not only for that use case, but for creating a new object with most (or all) of the properties of an existing object — which comes up a lot when you're updating state, since you can't modify state directly:
this.setState(prevState => {
return {foo: {...prevState.foo, a: "updated"}};
});
That replaces `this.state.foo` with a new object with all the same properties as `foo` except the `a` property, which becomes `"updated"`:
<!-- begin snippet: js hide: true console: true babel: false -->
<!-- language: lang-js -->
const obj = {
foo: {
a: 1,
b: 2,
c: 3
}
};
console.log("original", obj.foo);
// Creates a NEW object and assigns it to `obj.foo`
obj.foo = {...obj.foo, a: "updated"};
console.log("updated", obj.foo);
<!-- language: lang-css -->
.as-console-wrapper {
max-height: 100% !important;
}
<!-- end snippet -->
[1]: https://reactjs.org/docs/jsx-in-depth.html#children-in-jsx
