Function createUpdate

packages/core/src/SpringValue.ts:1105–1118

(props: any)

 *   or `null` if all keys are affected.
 */
export function createUpdate(props: any) {
  const { to, from } = (props = inferTo(props))

  // Collect the keys affected by this update.
  const keys = new Set<string>()

  if (is.obj(to)) findDefined(to, keys)
  if (is.obj(from)) findDefined(from, keys)

  // The "keys" prop helps in applying updates to affected keys only.
  props.keys = keys.size ? Array.from(keys) : null

  return props
}

/**
 * A modified version of `createUpdate` meant for declarative APIs.