Determine the total value of a specific key within a collection of objects

Question

Determine the total value of a specific key within a collection of objects

I am grappling with an array of objects:

let fileArray = [
  { filename: 'File1.txt', bytes: 12345, created: 1548360783511.728 },
  { filename: 'File2.txt', bytes: 34567, created: 1548361491237.182 },
  { filename: 'File3.txt', bytes: 23456, created: 1548361875763.893 },
  { filename: 'File4.txt', bytes: 56789, created: 1548360658932.682 }
];

I have two main objectives for this array: calculating the total bytes of all files in this array sum of numbers and identifying the file created first (smallest) Obtain smallest value from array in Javascript?.

I have considered using array.reduce(), however, it seems to be more suitable for flat arrays. Can it be used on specific keys of an array of objects, or would I need to create a temporary array containing all values for that key in the current array and then use array.reduce() on those values?

javascript arrays

Answer 1

Answer №1

Below is a demonstration of using the reduce() method to perform specific operations on an array. Two custom methods are defined to reduce the array: one for calculating the sum of bytes and another for finding the minimum created value. Finally, the array is reduced by invoking the respective custom reduce methods.

let fileArray = [
  {filename: 'File1.txt', bytes: 12345, created: 1548360783511.728},
  {filename: 'File2.txt', bytes: 34567, created: 1548361491237.182},
  {filename: 'File3.txt', bytes: 23456, created: 1548361875763.893},
  {filename: 'File4.txt', bytes: 56789, created: 1548360658932.682}
];

// Custom reduce method for calculating the sum of bytes.

const reduceWithSumBytes = (res, {bytes}) => res += bytes;

// Custom reduce method for finding the minimum created value.

const reduceWithMinCreated = (res, {created}) =>
{
    return res && (created < res ? created : res) || created;
};

// Perform reduce() operation using the custom methods.

console.log(fileArray.reduce(reduceWithSumBytes, 0));
console.log(fileArray.reduce(reduceWithMinCreated, null));

Answer 2

Below is a demonstration of using the reduce() method to perform specific operations on an array. Two custom methods are defined to reduce the array: one for calculating the sum of bytes and another for finding the minimum created value. Finally, the array is reduced by invoking the respective custom reduce methods.

let fileArray = [
  {filename: 'File1.txt', bytes: 12345, created: 1548360783511.728},
  {filename: 'File2.txt', bytes: 34567, created: 1548361491237.182},
  {filename: 'File3.txt', bytes: 23456, created: 1548361875763.893},
  {filename: 'File4.txt', bytes: 56789, created: 1548360658932.682}
];

// Custom reduce method for calculating the sum of bytes.

const reduceWithSumBytes = (res, {bytes}) => res += bytes;

// Custom reduce method for finding the minimum created value.

const reduceWithMinCreated = (res, {created}) =>
{
    return res && (created < res ? created : res) || created;
};

// Perform reduce() operation using the custom methods.

console.log(fileArray.reduce(reduceWithSumBytes, 0));
console.log(fileArray.reduce(reduceWithMinCreated, null));

Answer 3

Answer №2

Is this the traditional approach?

let totalSize = 0;
for(let index = 0; index < fileList.length; index++){
    totalSize += fileList[index].size;
}
console.log(totalSize);

Additionally,

let indexOfFirstFile = 0;
for(let index = 0; index < fileList.length; index++){
    if(fileList[index].created < fileList[indexOfFirstFile].created){
        indexOfFirstFile = index;
    }
}   
console.log(fileList[indexOfFirstFile].filename);

Answer 4

Is this the traditional approach?

let totalSize = 0;
for(let index = 0; index < fileList.length; index++){
    totalSize += fileList[index].size;
}
console.log(totalSize);

Additionally,

let indexOfFirstFile = 0;
for(let index = 0; index < fileList.length; index++){
    if(fileList[index].created < fileList[indexOfFirstFile].created){
        indexOfFirstFile = index;
    }
}   
console.log(fileList[indexOfFirstFile].filename);

Determine the total value of a specific key within a collection of objects

Answer №1

Answer №2

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