---
title: 动态 target
order: 15
---

target 动态变化

```jsx
import Overlay from '@alifd/overlay';

let idx = 0;
class Demo extends React.Component {
  constructor(props) {
    super(props);

    this.state = {
      visible: true,
      target: () => this.btn0,
    };
  }
  next = (idx) => {
    switch (idx) {
      case 0:
        this.setState({
          target: () => this.btn0,
        });
        break;
      case 1:
        this.setState({
          target: () => this.btn1,
        });
        break;
      case 2:
        this.setState({
          target: () => this.btn2,
        });
        break;
    }
  };

  onClick = () => {
    this.setState({
      visible: !this.state.visible,
    });
  };

  onClose = () => {
    this.setState({
      visible: false,
    });
  };

  render() {
    return (
      <div>
        <button onClick={this.onClick} ref={(ref) => (this.btn0 = ref)}>
          First
        </button>
        <button onClick={this.onClick} ref={(ref) => (this.btn1 = ref)} style={{ marginLeft: 500 }}>
          Second
        </button>
        <br />
        <button
          onClick={this.onClick}
          ref={(ref) => (this.btn2 = ref)}
          style={{ marginLeft: 500, marginTop: 400 }}
        >
          Third
        </button>
        <Overlay placement="b" visible={this.state.visible} target={this.state.target}>
          <span style={{ width: 300, height: 200, border: '1px solid' }}>
            Hello World From Overlay!
            <br />
            <br />
            <br />
            <br />
            <br />
            <br />
            <br />
            <button style={{ marginLeft: 200 }} onClick={() => this.next(++idx % 3)}>
              next
            </button>
          </span>
        </Overlay>
      </div>
    );
  }
}

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