moy-dom/src/listDiff/makeKeyIndexAndFree.js

A flexiable Virtual DOM library for building modern web interface.

export default function makeKeyIndexAndFree(list){
  const keyIndex = new Map(),
        free = []
  let itemKey

  for(let [index, item] of list.entries()){
    itemKey = item.key
    if(itemKey !== undefined){
      keyIndex.set(itemKey, index)
    }else{
      free.push(item)
    }
  }

  return {
    keyIndex,
    free,
  }
}