匹配对象数组中的对象键并返回具有最高音量值的值

Question

I have an array of objects, baseAsset key and Volume are part of every object but the volume is different for each object.

I want to match the baseAsset key and return the object with the highest volume value. Efficiency and speed is important as array have 3000+ objects

let tickerA = [{
    pair: 'AUDUSD',
    baseAsset: 'AUD',
    lastPriceUSD: 0.74,
    volume: 1000
}, {
    pair: 'AUDUSD',
    baseAsset: 'AUD',
    lastPriceUSD: 0.76,
    volume: 2000
}, {
    pair: 'USDEUR',
    baseAsset: 'USD',
    lastPriceUSD: 1.25,
    volume: 1200
}, {
    pair: 'USDEUR',
    baseAsset: 'USD',
    lastPriceUSD: 1.19,
    volume: 1500
}]

Expected return from a function

tickerB = [{
    baseAsset: 'AUD',
    lastPriceUSD: 0.76,
    volume: 2000
}, {
    baseAsset: 'USD',
    lastPriceUSD: 1.25,
    volume: 1500
}]

Answer 1

You can do this in O(n) time by looping over and saving the largest item to an object. In the end your values will be in the Object.values of the groups:

 let tickerA = [{pair: 'AUDUSD',baseAsset: 'AUD',lastPriceUSD: 0.74,volume: 1000}, {pair: 'AUDUSD',baseAsset: 'AUD',lastPriceUSD: 0.76,volume: 2000}, {pair: 'USDEUR',baseAsset: 'USD',lastPriceUSD: 1.25,volume: 1200}, {pair: 'USDEUR',baseAsset: 'USD',lastPriceUSD: 1.19,volume: 1500}] let groups = tickerA.reduce((largest, {baseAsset, lastPriceUSD, volume}) => { /* * if it's a new baseAsset or bigger than a previous one, save it * to the group under the baseAsset key */ if (!largest[baseAsset] || largest[baseAsset]['volume'] < volume ) { largest[baseAsset] = {baseAsset, lastPriceUSD, volume} } return largest }, {}) TickerB = Object.values(groups) console.log(TickerB) 

Answer 2

One approach would be to iterate the values of tickerA and map these to baseAsset keys if that item's volume value is greater than that of the current item of that baseAsset key:

 let tickerA = [{ pair: 'AUDUSD', baseAsset: 'AUD', lastPriceUSD: 0.74, volume: 1000 }, { pair: 'AUDUSD', baseAsset: 'AUD', lastPriceUSD: 0.76, volume: 2000 }, { pair: 'USDEUR', baseAsset: 'USD', lastPriceUSD: 1.25, volume: 1200 }, { pair: 'USDEUR', baseAsset: 'USD', lastPriceUSD: 1.19, volume: 1500 }]; /* Use map to relate baseAsset key of tickerA item with current max volume value */ const map = new Map() /* Iterate tickerA items, searching for greatest volume value per baseAsset class */ for(const item of tickerA) { const assetMatch = map.get(item.baseAsset); if(assetMatch && item.volume < assetMatch.volume) { /* If matching item (by asset found) with volume greater than that of current tickerA item, then disregard the current item */ continue; } else { /* Otherwise, this tickerA item is; the first of the asset class, or greater in volume so we'll update the map entry for this asset class */ map.set(item.baseAsset, item); } } /* Extract the map values as an array */ const tickerB = Array.from(map.values()); console.log(tickerB); 

Answer 3

This alternative groups baseAsset and at the end extracts the grouped values.

This is a O(n) time complexity .

 let tickerA = [{pair: 'AUDUSD',baseAsset: 'AUD',lastPriceUSD: 0.74,volume: 1000}, {pair: 'AUDUSD',baseAsset: 'AUD',lastPriceUSD: 0.76,volume: 2000}, {pair: 'USDEUR',baseAsset: 'USD',lastPriceUSD: 1.25,volume: 1200}, {pair: 'USDEUR',baseAsset: 'USD',lastPriceUSD: 1.19,volume: 1500}]; let result = Object.values(tickerA.reduce((a, {baseAsset, lastPriceUSD, volume}) => { let {volume: current} = a[baseAsset] || {volume: Number.MAX_SAFE_INTEGER}; if (current < volume) a[baseAsset].volume = volume; else a[baseAsset] = {baseAsset, lastPriceUSD, volume}; return a; }, Object.create(null))); console.log(result); 

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Answer 4

Use reduce and Object.values :

 let tickerA = [{pair: 'AUDUSD',baseAsset: 'AUD',lastPriceUSD: 0.74,volume: 1000}, {pair: 'AUDUSD',baseAsset: 'AUD',lastPriceUSD: 0.76,volume: 2000}, {pair: 'USDEUR',baseAsset: 'USD',lastPriceUSD: 1.25,volume: 1200}, {pair: 'USDEUR',baseAsset: 'USD',lastPriceUSD: 1.19,volume: 1500}]; const res = Object.values(tickerA.reduce((acc, { baseAsset, lastPriceUSD, volume }) => { acc[baseAsset] = (!acc[baseAsset] || acc[baseAsset].volume < volume) ? { baseAsset, lastPriceUSD, volume } : acc[baseAsset]; return acc; }, {})); console.log(res); 

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