recyling.js

/**
 * Having a constructor tells the VM that this object as a given "shape".
 * If this shape is constant, all the code manipulating it will eventually
 * be optimized into specialized stubs. This has a HUGE performance impact
 * and that's why sometimes JavaScript can be so close to the metal.
 */
function VNode(tag, data, children) {
  this.tag = tag
  this.data = data
  this.children = children || []
}

/**
 * This holds trashed vnodes that are not used anymore.
 * Wee keep them here to be able to re-use them later. As we keep a reference
 * to them here, GC won't try to collect them. No collection = GOOD.
 */
const nodePool = []

const setNode = (vnode, tag, data, children) => {
  vnode.tag = tag
  vnode.data = data
  vnode.children = children
  return vnode
}

/**
 * This first try to take a trashed vnode and recycle it (assing new properties
 * to it). The advatage of doing so is that it's a cheap operation, no allocation
 * is happening here, only assignements.
 */
const recycleNode = (tag, data, children) => (
  nodePool.length > 0
    ? setNode(nodePool.pop(), tag, data, children)
    : new VNode(tag, data, children)
)

const collectNode = (vnode) => {
  nodePool.push(vnode)
}