避免 obj.xxx && obj.xxx.length 这样的写法

store

import * as u from "lodash";

function isEmpty(opt) {

  return function(target, key, des) {

    if (!opt) opt = `is${u.upperFirst(key)}`;

    Object.defineProperty(target, opt, {

      get: function proxyGetter() {

        return !u.isEmpty(this[key]);

      },

      enumerable: true,

      configurable: true,

    });

  };

}

class IndexStore {

  @observable

  @isEmpty()

  lst = null;

}

组件

@inject("indexStore")

@observer

class Test extends Component {

  componentDidMount() {

    setTimeout(() => {

      this.props.indexStore.lst = ["a", "b"];

    }, 2000);

    setTimeout(() => {

      this.props.indexStore.lst = null;

    }, 4000);

  }

  render() {

    const { indexStore } = this.props;

    return (

        <ul>

          {indexStore.isLst && indexStore.lst.map(el => <li key={el}>{el}</li>)}

        </ul>

    );

  }

}