函数调用前的@是什么意思？

Question

Link to project referred to link 项目有一个名为 connectToStores 的函数，它像这样导入（使用 es6 语法）

import connectToStores from '../utils/connectToStores';

然而，当它被调用时（见上文link），有一个@放在前面

@connectToStores([RepoStore, StargazersByRepoStore, UserStore], getState)

原来的connectToStores函数是一个看似常规的导出函数。为什么前面有@？

export default function connectToStores(stores, getState) {
  return function (DecoratedComponent) {
    const displayName =
      DecoratedComponent.displayName ||
      DecoratedComponent.name ||
      'Component';

    return class StoreConnector extends Component {
      static displayName = `connectToStores(${displayName})`;

      constructor(props) {
        super(props);
        this.handleStoresChanged = this.handleStoresChanged.bind(this);

        this.state = getState(props);
      }

      componentWillMount() {
        stores.forEach(store =>
          store.addChangeListener(this.handleStoresChanged)
        );
      }

      componentWillReceiveProps(nextProps) {
        if (!shallowEqual(nextProps, this.props)) {
          this.setState(getState(nextProps));
        }
      }

      componentWillUnmount() {
        stores.forEach(store =>
          store.removeChangeListener(this.handleStoresChanged)
        );
      }

      handleStoresChanged() {
        this.setState(getState(this.props));
      }

      render() {
        return <DecoratedComponent {...this.props} {...this.state} />;
      }
    };
  };
}

Answer 1

那些 @ 是 ES7 decorators (they are transpiled through Babel)。来自规范：

It is also possible to decorate a class. In this case, the decorator takes the target constructor.

// A simple decorator
@annotation
class MyClass { }

function annotation(target) {
   // Add a property on target
   target.annotated = true;
}

函数调用前的@是什么意思？

What does the @ in front of a function call mean?

javascript

ecmascript-6

reactjs

babeljs