Question 266857 in Javascript Question posted in
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Javascript – Need help optimizing a loop of merging objects and arrays

heres a working example of what I’m trying to do:

  private mergeData(dataArray) {
    const mergedData = {
      items: [],
      money: {
        money1: 0,
        money2: 0,
        money3: 0,
      }
    }
    for (const data of dataArray) {
      mergedData.money.money1 += data.money.money1
      mergedData.money.money2 += data.money.money2
      mergedData.money.money3 += data.money.money3
      mergedData.items = [...mergedData.items, ...data.items]
    }

    return mergedData
  }

I’m looking to optimize this as something about it feels smelly.

I have Lodash available in my project and would ideally use it if possible.

I would like to add more details as I seem to have posted this too hastily

dataArray looks like an array of these objects

{
      items: [],
      money: {
        money1: 0,
        money2: 0,
        money3: 0,
      }
    }

And items is just an object with string key:value pairs

I’m looking to make this more concise and possibly optimize performance on item merging

Thanks.

Tags:

3

Answers


  1. 0

    You can use reduce

    private mergeData(dataArray) {
  const mergedData = {
    items: [],
    money: {
      money1: 0,
      money2: 0,
      money3: 0,
    }
  }

  return dataArray.reduce((acc, curr) => {
    acc.items.push(...curr.items)
    acc.money.money1 += curr.money.money1
    acc.money.money2 += curr.money.money2
    acc.money.money3 += curr.money.money3
    return acc;

  }, mergedData)

}
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  2. 0

    You can optimize the merging of the array of objects using lodash’s _.mergeWith() function to merge the "money" properties and _.concat() to merge the "items" arrays. Here’s an example of how you can do it:

    const _ = require('lodash');

function mergeData(dataArray) {
  const mergedData = {
    items: [],
    money: {
      money1: 0,
      money2: 0,
      money3: 0,
    },
  };

  for (const data of dataArray) {
    // Merge "money" properties
    _.mergeWith(mergedData.money, data.money, (objValue, srcValue) => objValue + srcValue);

    // Concatenate "items" arrays
    mergedData.items = _.concat(mergedData.items, data.items);
  }

  return mergedData;
}

// Example dataArray
const dataArray = [
  {
    items: [{ key1: 'value1' }],
    money: {
      money1: 10,
      money2: 20,
      money3: 30,
    },
  },
  {
    items: [{ key2: 'value2' }],
    money: {
      money1: 5,
      money2: 15,
      money3: 25,
    },
  },
];

const mergedData = mergeData(dataArray);
console.log(mergedData);
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  3. 0

    I would simplify the code using the following 2 points.

    1. Reuse the items array instead of creating a new one each iteration. This can be done by pushing data.items into the existing array.

      items.push(...data.items);

    2. Collect the money keys in a separate array before you start looping dataArray.

        const moneyKeys = Object.keys(money)

      Then add the values of the listed keys to the total for each data.money in dataArray.

      moneyKeys.forEach(key => money[key] += data.money[key])

    function mergeData(dataArray) {
  const items = [];
  const money = { money1: 0, money2: 0, money3: 0 };
  const moneyKeys = Object.keys(money);
  
  for (const data of dataArray) {
    items.push(...data.items);
    moneyKeys.forEach(key => money[key] += data.money[key]);
  }
  
  return { items, money };
}

console.log(mergeData([
  {
    items: ['a', 'b', 'c'],
    money: { money1: 2, money2: 4, money3: 8 },
  }, {
    items: ['x', 'y', 'z'],
    money: { money1: 1, money2: 2, money3: 3 },
  }
]));

    You can replace the for...of loop with something faster if you really need the additional speed.

    ps. If possible I would personally replace { money1: 0, money2: 0, money3: 0 } with a simple array [0, 0, 0]. As soon as you start numbering your attributes you probably want to use an array instead. This only works if you have control over the build process of the input structure.

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