examples

plus/minus

html

<button data-s="down">-</button>
<span data-r="up down">0</span>
<button data-s="up">+</button>

javascript

export const b = {};

export function down(_, __, el) {
  el.innerHTML = el.innerHTMLAsInt() - 1;
}

export function up(_, __, el) {
  el.innerHTML = el.innerHTMLAsInt() + 1;
}

styles

[data-r~=up] {
  display: inline-block;
  text-align: center;
  width: 3rem; 
}