IIUC this is how VanJS works.

  // Create new Ref
  const r = van.state(0)
  // derive functions as adapt/watch/multiplex.
  // Implicitly depends on any Ref it uses and re-runs when they change.
  const r2 = van.derive(() => 2 * r.val)
  van.derive(() => console.log('r2 is ' + r2.val))
  
  // Changing the value doesn't update r2 or print immediately, it schedules
  // a batch update when all derives will get recomputed.
  r.val = 3
  // ...So 'r2 is 6' won't be printed here.
  r.val++
  
  // Refs can be used in a hyperscript-style DOM builder.
  // This creates a regular HTMLElement, with a regular Text node where r2 goes,
  // but it holds onto that Text node behind the scenes and automatically
  // updates it when r2 changes.
  const {p} = van.tags
  document.appendChild(p("The value is ", r2))