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Score: 1; Reported for: Exact paragraph match Open both answers

Possible Plagiarism

Plagiarized on 2020-05-12
by DBL

Original Post

Original - Posted on 2015-06-25
by T.J. Crowder

Present in both answers; Present only in the new answer; Present only in the old answer;

See comments in code:
<!-- begin snippet: js hide: false console: true babel: true -->
<!-- language: lang-js -->
class App extends React.Component { constructor(props) { super(props); this.state = { buttonsList: [], btnCounter: 0, } }
addButton = () => { // you can pass name, value for new button based on some value const id = new Date().getTime(); // you can also generate new id every time // use functional setState whenever update previous state this.setState((prevState) => ({ btnCounter: prevState.btnCounter + 1, buttonsList: [...prevState.buttonsList, { id: prevState.btnCounter + 1, name: `Name${prevState.btnCounter + 1}`, value: `Send Option` }] })); // if possible add properties of button instead of directly adding element into state }
sendOption = (buttonId) => { console.log(buttonId) }
render() { const { buttonsList } = this.state; return ( <div> <button onClick={this.addButton}>Add new Button</button> {buttonsList && buttonsList.length > 0 &&, i) => ( <div key={}> <button name={} onClick={() => this.sendOption(} > {btn.value} </button> </div> ))} </div> ); } }
ReactDOM.render(<App />, document.getElementById('root'));
<!-- language: lang-html -->
<script src=""></script> <script src=""></script> <div id="root"></div>

<!-- end snippet -->

That's [*property spread notation*][1]. It was added in ES2018 (spread for arrays/iterables was earlier, ES2015), but it's been supported in React projects for a long time via transpilation (as "[JSX spread attributes][2]" even though you could do it elsewhere, too, not just attributes).
`{...this.props}` *spreads out* the "own" enumerable 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&nbsp;&mdash; the good kind&nbsp;&mdash; 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=""></script> <script src=""></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&nbsp;&mdash; which comes up a lot when you're updating state, since you can't modify state directly:
this.setState(prevState => { return {foo: {, a: "updated"}}; });
That replaces `` 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",; // Creates a NEW object and assigns it to `` = {, a: "updated"}; console.log("updated",;

<!-- language: lang-css -->
.as-console-wrapper { max-height: 100% !important; }
<!-- end snippet -->

[1]: [2]:

Present in both answers; Present only in the new answer; Present only in the old answer;