Three dots .... Expand operator

In React:

That's property spread notation. 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" 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}>

https://stackoverflow.com/questions/31048953/what-do-these-three-dots-in-react-do

In JS:

var obj = Object.assign({}, ...array)

https://stackoverflow.com/questions/38985624/alternative-of-object-assign-array