react without constructor declaring state in class's body

Question

I saw below code somewhere and I'm curious. It looks cleaned but unusual to me. Why state = {} is declared without an constructor?

and load declared without a function keyword? As I know for there are ways to write a function

function async load() {} or const async load = ()=>{}

And what ...args does? is it spread arguments?

import View from './View';
import loadData from './loadData';
export default class extends Component {
  state = {};
  load = this.load.bind(this);
  async load(...args) {
    try {
      this.setState({ loading: true, error: false });
      const data = await loadData(...args);
      this.setState({ loading: false, data });
    } catch (ex) {
      this.setState({ loading: false, error: true });
    }
  }
  render() {
    return (
      <View {...this.props} {...this.state} onLoad={this.load} />
    );
  }
}

Answer 1

The state = {} declaration is a class property, which is currently not part of the JavaScript language. Certain utilities such as Babel will compile this into legal JavaScript code.

However, the lack of a function keyword within classes, as well as the ... operator are part of ECMAScript 6, which has been officially implemented into the language (though some browsers do not recognize it yet).

Class Definition
Spread Operator