What is the method for combining sub-subarrays and calculating their total length based on their sub-array index?

Question

What is the method for combining sub-subarrays and calculating their total length based on their sub-array index?

I am dealing with an array that contains sub-arrays, each of which may have different lengths. For example:

let arrayA = [
              [['a']            , ['b','c','d']],  //lengths  1  and  3 
              [['e','f','g','z'], ['h','i','j']],  //lengths  4  and  3
              [['k','l']        , ['m','n']]       //lengths  2  and  2 
                                                   //sums     7  and  8
             ]

The goal is to calculate the sum of the lengths of each sub-subarray based on the index of the sub-array it belongs to:

let arrayB = [[7],[8]]

What would be the most effective approach to accomplish this task?

javascript arrays sub-array

Answer 1

Answer №1

To easily summarize the array, you can utilize the reduce function. For iterating through the inner array, you can use forEach.

let arrayWithNestedArrays = [[["a"],["b","c","d"]],[["e","f","g","z"],["h","i","j"]],[["k","l"],["m","n"]]];

let finalResult = arrayWithNestedArrays.reduce((accumulator, currentValue) => {
  currentValue.forEach((object, index) => {
    accumulator[index] = accumulator[index] || [0];
    accumulator[index][0] += object.length;
  })
  return accumulator;
}, []);

console.log(finalResult);

Answer 2

To easily summarize the array, you can utilize the reduce function. For iterating through the inner array, you can use forEach.

let arrayWithNestedArrays = [[["a"],["b","c","d"]],[["e","f","g","z"],["h","i","j"]],[["k","l"],["m","n"]]];

let finalResult = arrayWithNestedArrays.reduce((accumulator, currentValue) => {
  currentValue.forEach((object, index) => {
    accumulator[index] = accumulator[index] || [0];
    accumulator[index][0] += object.length;
  })
  return accumulator;
}, []);

console.log(finalResult);

Answer 3

Answer №2

To make the array smaller, you can use the `length` property to calculate the sum when mapping through it. After that, encapsulate the results in a new array.

var array = [[['a'], ['b', 'c', 'd']], [['e', 'f', 'g', 'z'], ['h', 'i', 'j',]], [['k', 'l'], ['m', 'n']]],
    result = array
        .reduce((r, a) => a.map(({ length }, i) => (r[i] || 0) + length), [])
        .map(a => [a]);

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 4

To make the array smaller, you can use the `length` property to calculate the sum when mapping through it. After that, encapsulate the results in a new array.

var array = [[['a'], ['b', 'c', 'd']], [['e', 'f', 'g', 'z'], ['h', 'i', 'j',]], [['k', 'l'], ['m', 'n']]],
    result = array
        .reduce((r, a) => a.map(({ length }, i) => (r[i] || 0) + length), [])
        .map(a => [a]);

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 5

Answer №3

Start by creating a new array containing the length of only the first sub-array from the original array. Next, use the slice method to create another array consisting of elements from index 1 up to its length from the original array.

Then iterate over the arrays using the forEach method and access the index within the loop.

let arrayA = [
  [
    ['a'],
    ['b', 'c', 'd']
  ],
  [
    ['e', 'f', 'g', 'z'],
    ['h', 'i', 'j', ]
  ],
  [
    ['k', 'l'],
    ['m', 'n']
  ]
]

let initialElem = arrayA[0].map((item) => {
  return [item.length]
})
let secElem = arrayA.slice(1, arrayA.length).forEach(function(item, index) {
  if (Array.isArray(item)) {
    item.forEach(function(elem, index2) {
      initialElem[index2][0] = initialElem[index2][0] + elem.length
    })
  }

})
console.log(initialElem)

Answer 6

Start by creating a new array containing the length of only the first sub-array from the original array. Next, use the slice method to create another array consisting of elements from index 1 up to its length from the original array.

Then iterate over the arrays using the forEach method and access the index within the loop.

let arrayA = [
  [
    ['a'],
    ['b', 'c', 'd']
  ],
  [
    ['e', 'f', 'g', 'z'],
    ['h', 'i', 'j', ]
  ],
  [
    ['k', 'l'],
    ['m', 'n']
  ]
]

let initialElem = arrayA[0].map((item) => {
  return [item.length]
})
let secElem = arrayA.slice(1, arrayA.length).forEach(function(item, index) {
  if (Array.isArray(item)) {
    item.forEach(function(elem, index2) {
      initialElem[index2][0] = initialElem[index2][0] + elem.length
    })
  }

})
console.log(initialElem)

What is the method for combining sub-subarrays and calculating their total length based on their sub-array index?

Answer №1

Answer №2

Answer №3

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