<input type="checkbox" checked>

document.getElementById("myCheckbox").checked = true;

$("#myCheckbox").prop("checked", true);

class MyCheckbox extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      isChecked: true
    };
  }

  handleChange = () => {
    this.setState({ isChecked: !this.state.isChecked });
  }

  render() {
    return (
      <input
        type="checkbox"
        checked={this.state.isChecked}
        onChange={this.handleChange}
      />
    );
  }
}