ES6 Last Item in Map()

getLastInMap.js

// Since ES6 Map()'s' retain their order of insertion, it can sometimes be useful to get the last item or value inserted:

export const getLastItemInMap = map => Array.from(map)[map.size-1]
export const getLastKeyInMap = map => Array.from(map)[map.size-1][0]
export const getLastValueInMap = map => Array.from(map)[map.size-1][1]

// Obviously getLastKey and getLastValue can reuse getLastItem, but for maximum portability I opted for verbosity.

const [lastKey, lastValue] = [...map].at(-1) || []
// Key only
const [lastKey] = [...map].at(-1) || []
// Value only
const [, lastValue] = [...map].at(-1) || []
// set
const lastValue = [...set].at(-1)