lit动态修改样式

src/my-counter.ts:

import { LitElement, css, html } from "lit";
import { customElement, property } from "lit/decorators.js";
import { styleMap } from "lit/directives/style-map.js";

@customElement("my-counter")
export class MyCounter extends LitElement {
	@property({ type: Number })
	count = 0;

	render() {
		const styles = { color: "" };
		if (this.count >= 0) {
			styles.color = "green";
		} else {
			styles.color = "red";
		}
		return html`
      <div>
        <button @click=${this._onDec} type="button"> - </button>
        count is: <span style=${styleMap(styles)}>${this.count}</span>
        <button @click=${this._onInc} type="button"> + </button>
      </div>
    `;
	}

	private _onDec() {
		this.count--;
	}

	private _onInc() {
		this.count++;
	}

	static styles = css`
    button {
      border-radius: 4px;
      border: 1px solid transparent;
      background-color: limegreen;
    }
  `;
}

declare global {
	interface HTMLElementTagNameMap {
		"my-counter": MyCounter;
	}
}

index.html:

<!doctype html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <link rel="icon" type="image/svg+xml" href="/vite.svg" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Vite + Lit + TS</title>
    <script type="module" src="/src/my-counter.ts"></script>
  </head>
  <body>
    <my-counter count="5"></my-counter>
    <my-counter count="-5"></my-counter>
  </body>
</html>