Function prepareSprings

packages/core/src/Controller.ts:566–577

* Ensure spring objects exist for each defined key. * * Using the `props`, the `Animated` node of each `SpringValue` may * be created or updated.

(
  springs: SpringValues,
  props: ControllerQueue[number],
  create: (key: string) => SpringValue
)

 * be created or updated.
 */
function prepareSprings(
  springs: SpringValues,
  props: ControllerQueue[number],
  create: (key: string) => SpringValue
) {
  if (props.keys) {
    each(props.keys, key => {
      const spring = springs[key] || (springs[key] = create(key))
      spring['_prepareNode'](props)
    })
  }
}

/**
 * Ensure spring objects exist for each defined key, and attach the