ant-design/components/tree-select/demo/async.md

---
order: 5
title:
  zh-CN: 异步加载
  en-US: Asynchronous loading
---

## zh-CN

异步加载树节点。

## en-US

Asynchronous loading tree node.

```jsx
import { TreeSelect } from 'antd';

class Demo extends React.Component {
  state = {
    value: undefined,
    treeData: [
      { id: 1, pId: 0, value: '1', title: 'Expand to load' },
      { id: 2, pId: 0, value: '2', title: 'Expand to load' },
      { id: 3, pId: 0, value: '3', title: 'Tree Node', isLeaf: true },
    ],
  };

  genTreeNode = (parentId, isLeaf = false) => {
    const random = Math.random()
      .toString(36)
      .substring(2, 6);
    return {
      id: random,
      pId: parentId,
      value: random,
      title: isLeaf ? 'Tree Node' : 'Expand to load',
      isLeaf,
    };
  };

  onLoadData = treeNode =>
    new Promise(resolve => {
      const { id } = treeNode.props;
      setTimeout(() => {
        this.setState({
          treeData: this.state.treeData.concat([
            this.genTreeNode(id, false),
            this.genTreeNode(id, true),
          ]),
        });
        resolve();
      }, 300);
    });

  onChange = value => {
    console.log(value);
    this.setState({ value });
  };

  render() {
    const { treeData } = this.state;
    return (
      <TreeSelect
        treeDataSimpleMode
        style={{ width: 300 }}
        value={this.state.value}
        dropdownStyle={{ maxHeight: 400, overflow: 'auto' }}
        placeholder="Please select"
        onChange={this.onChange}
        loadData={this.onLoadData}
        treeData={treeData}
      />
    );
  }
}

ReactDOM.render(<Demo />, mountNode);
```