how to return one index object of an array (instead of the entire array)

Question

I've written some code that looks like:

state.intro = state.memoryCards[Math.floor(Math.random() * state.memoryCards.length)];

I don't think this is the right way to mutate the state, so I was refactoring the code below, but i am not sure how to return one index of that memoryCards array.


 intro: state.memoryCards.find(function(card, index) {
                    const randomIndex = Math.floor(Math.random() * state.memoryCards.length);
                    if(index === randomIndex) {
                        return card
                    }
                })

is this a redux reducer or is state the state of a React component? — pteranobyte
– pteranobyte, Commented Jun 24, 2019 at 21:22

pteranobyte · Accepted Answer · 2019-06-26 11:40:36Z

1

I think you mean

state.memoryCards.find(
    (card, index) => index === Math.floor(
        Math.random() * state.memoryCards.length
    )
).type

(but I'm not sure I understand what you want)

edited Jun 26, 2019 at 11:40

answered Jun 24, 2019 at 21:28

pteranobyte

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2 Comments

frontend Over a year ago

But is that good to have a math random method inside a reducer

pteranobyte Over a year ago

yeah there's nothing wrong with using Math.random inside a reducer in principal, if you actually want that random choice put into the store, and that random choice needs to be accessed from various parts of the app. However, I think in most cases which require you to select a random element from state you would do that in a selector rather than a reducer.

Benjamin Charais · Accepted Answer · 2019-06-27 05:54:31Z

0

In this case it comes down to what method you are looking to return from the array itself.

Map will return an array that is the same length as the one being looked over, Find as a method will return the first element that passes the input test for the array.

You had the proper spread on state, so that previous state is input into the return first, and then it overwrite memoryCards with the new one, and (I'm guessing...) inputs the rest of the memoryCards that are in that object, and overwrites the specific index with the next type value

Edit: return only one value for memoryCards

intro: state.memoryCards.find((card, index) => {
    const randomCard = Math.floor(Math.random() * state.memoryCards.length)
    if(index === randomCard) {
        return {
            ...state,
            memoryCards: card.type
        }
    }
})

edited Jun 27, 2019 at 5:54

answered Jun 24, 2019 at 21:51

Benjamin Charais

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2 Comments

frontend Over a year ago

but i want one value instead of the entire array.

Benjamin Charais Over a year ago

I'll update my answer to only return a single value.

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