Lit-element: How can I know slot is slotted?

[sheweichun]

import { LitElement, html,customElements } from 'lit-element';


class MyElement extends LitElement {

  render(){
    const {slotted} = this;  //how to get this slotted variable
    return html`
      <p>
          <slot></slot>
           ${slotted ? 'has slot' : 'no slot'}
      </p>
    `;
  }
}
customElements.define('my-element', MyElement);
```html
<my-elemen></my-elemen>
<my-elemen>test</my-elemen>

1. Question
   in MyElement' render function, how can I get a variable to tell me the slot is slotted?

[sorvell]

By "slotted" do you mean that element children have been assigned to the slot? I'm going to assume that's the case.

To see what elements are assigned to a <slot>, call assignedNodes() on the slot (docs).

To be informed of of changes to the assignedNodes() of a slot, you can listen to the slotchange event on the <slot> (docs).