TIL you can emulate the as const type suffix in JS with a helper function. (source)

/**
 * Identity function. Coerces string/number literals to value-as-type.
 * @template {string|number} T
 * @param {T} v
 * @return {T}
 */
function toConst(v) {
  return v;
}

const five = toConst(5);
// --> Type shows up as 5 instead of "number"