In my poker app I have an array of hands, each hand being array of randomly selected card objects with value and suit:
[ [ { value: 5, suit: 's' },
{ value: 4, suit: 's' },
{ value: 6, suit: 'c' },
{ value: 11, suit: 'd' },
{ value: 12, suit: 'c' } ],
[ { value: 9, suit: 'd' },
{ value: 12, suit: 'h' },
{ value: 8, suit: 'c' },
{ value: 12, suit: 's' },
{ value: 2, suit: 's' } ],
[ { value: 4, suit: 'h' },
{ value: 6, suit: 's' },
{ value: 10, suit: 'c' },
{ value: 3, suit: 'd' },
{ value: 7, suit: 'd' } ] ]
To prepare the hands for evaluation I want to use Array.reduce to return an array of hand objects. So the output would be:
[
{
values: [5, 4, 6, 11, 12],
suits: ['s', 's', 'c', 'd', 'c']
},
{
values: [9, 12, 8, 12, 2],
suits: ['d', 'h', 'c', 's', 's']
},
{
values: [4, 6, 10, 3, 7],
suits: ['h', 's', 'c', 'd', 'd']
}
]
I tried implementing this with nested forEach's, but its failing and I don't know why. I have two console.log's within which output as expected, but in the end hands is identical to the input.
let temp = []
hands.forEach((el) => {
temp = el
el = {}
el.values = []
el.suits = []
console.log(el) //expected output
temp.forEach((obj) => {
el.values.push(obj.value)
el.suits.push(obj.suit)
console.log(el) //expected output
})
})
console.log(hands) //same as original
You have to be thinking about the shape of your input data (DATA
) and output (DATA'
)
Note 1:1 relationship between HAND
and HAND'
meaning we will use Array.prototype.map
for one transformation. On the other hand, CARD
has a N:1 relationship with HAND'
meaing we will use Array.prototype.reduce
for that transformation
So keep in mind while we're working, we will be doing a map and a reduce
const data =
[ [ { value: 5, suit: 's' },
{ value: 4, suit: 's' },
{ value: 6, suit: 'c' },
{ value: 11, suit: 'd' },
{ value: 12, suit: 'c' } ],
[ { value: 9, suit: 'd' },
{ value: 12, suit: 'h' },
{ value: 8, suit: 'c' },
{ value: 12, suit: 's' },
{ value: 2, suit: 's' } ],
[ { value: 4, suit: 'h' },
{ value: 6, suit: 's' },
{ value: 10, suit: 'c' },
{ value: 3, suit: 'd' },
{ value: 7, suit: 'd' } ] ]
let output =
data.map(cards =>
cards.reduce(({values, suits}, {value, suit}) => ({
values: [...values, value],
suits: [...suits, suit]
}), {values: [], suits: []}))
console.log(output)
Now of course that looks a little dense so it would be nice if we could dial down the complexity a bit. By making some curried adapters for map
and reduce
we can express a function that performs your transformation quite nicely
const data =
[ [ { value: 5, suit: 's' },
{ value: 4, suit: 's' },
{ value: 6, suit: 'c' },
{ value: 11, suit: 'd' },
{ value: 12, suit: 'c' } ],
[ { value: 9, suit: 'd' },
{ value: 12, suit: 'h' },
{ value: 8, suit: 'c' },
{ value: 12, suit: 's' },
{ value: 2, suit: 's' } ],
[ { value: 4, suit: 'h' },
{ value: 6, suit: 's' },
{ value: 10, suit: 'c' },
{ value: 3, suit: 'd' },
{ value: 7, suit: 'd' } ] ]
const map = f => xs => xs.map(f)
const reduce = f => y => xs => xs.reduce(f, y)
const handAppendCard = ({values, suits}, {value, suit}) => ({
values: [...values, value],
suits: [...suits, suit]
})
const makeHands =
map (reduce (handAppendCard) ({values:[], suits:[]}))
let output = makeHands (data)
console.log(output)
That's just one way to approach the problem. I hope you were able to learn something from it ^_^