Is there a way to retrieve the final elements from a deeply nested array?

Question

Is there a way to retrieve the final elements from a deeply nested array?

I've been struggling to extract the last item from a nested array of objects. I've tried using methods like flatMap, flat, filter, and splice, but so far haven't had any luck getting the desired array.

const array = [
  [
    {
      total_cases: 18,
    },
    {
      total_cases: 32,
    },
    {
      total_cases: 7,
    },
  ],
  [
    {
      total_cases: 4,
    },
    {
      total_cases: 52,
    },
  ],
  [
    {
      total_cases: 68,
    },
  ],
];

The provided array structure is shown above. Can anyone suggest a way to extract only the last object's total_cases value into a new array?

The expected new array should look like this:

[7, 52, 68]

Your assistance is greatly appreciated!

javascript arrays object nested

Answer 1

Answer №1

Update according to the revised question.

To extract only the last element of each nested array and then retrieve the total_cases values, you can employ methods such as map, slice, and flat:

const array = [
  [ 
    { total_cases: 18 },
    { total_cases: 32 },
    { total_cases: 7 },
  ],
  [ 
    { total_cases: 4 },
    { total_cases: 52 },
  ],
  [ 
    { total_cases: 68 },
  ],
];

const result = array
  .map(a => a.slice(a.length - 1))
  .flat(1)
  .map(o => o.total_cases)
  
console.log(result)

Initial Response

You may flatten the array, filter it based on the date attribute, and then use map to get the total_cases values:

const array = [
  [
    {
      date: "2020-02-25",
      total_cases: 18,
    },
    {
      date: "2020-02-26",
      total_cases: 32,
    },
    {
      date: "last-object",
      total_cases: 7,
    },
  ],
  [
    {
      date: "2020-02-26",
      total_cases: 4,
    },
    {
      date: "last-object",
      total_cases: 52,
    },
  ],
  [
    {
      date: "last-object",
      total_cases: 68,
    },
  ],
];

const result = array
  .flat(1)
  .filter(o => o.date == 'last-object')
  .map(o => o.total_cases)
  
console.log(result)

Answer 2

Update according to the revised question.

To extract only the last element of each nested array and then retrieve the total_cases values, you can employ methods such as map, slice, and flat:

const array = [
  [ 
    { total_cases: 18 },
    { total_cases: 32 },
    { total_cases: 7 },
  ],
  [ 
    { total_cases: 4 },
    { total_cases: 52 },
  ],
  [ 
    { total_cases: 68 },
  ],
];

const result = array
  .map(a => a.slice(a.length - 1))
  .flat(1)
  .map(o => o.total_cases)
  
console.log(result)

Initial Response

You may flatten the array, filter it based on the date attribute, and then use map to get the total_cases values:

const array = [
  [
    {
      date: "2020-02-25",
      total_cases: 18,
    },
    {
      date: "2020-02-26",
      total_cases: 32,
    },
    {
      date: "last-object",
      total_cases: 7,
    },
  ],
  [
    {
      date: "2020-02-26",
      total_cases: 4,
    },
    {
      date: "last-object",
      total_cases: 52,
    },
  ],
  [
    {
      date: "last-object",
      total_cases: 68,
    },
  ],
];

const result = array
  .flat(1)
  .filter(o => o.date == 'last-object')
  .map(o => o.total_cases)
  
console.log(result)

Answer 3

Answer №2

To fetch the last element of an array, you can utilize the .at() method with a negative parameter. This method allows you to count back from the end of the array. For example, using .at(-1) will return the last element in the array.

const array=[[{total_cases:18},{total_cases:32},{total_cases:7}],[{total_cases:4},{total_cases:52}],[{total_cases:68}]];

const result = array.map(e => e.at(-1).total_cases);

console.log(...result);

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

Answer 4

To fetch the last element of an array, you can utilize the .at() method with a negative parameter. This method allows you to count back from the end of the array. For example, using .at(-1) will return the last element in the array.

const array=[[{total_cases:18},{total_cases:32},{total_cases:7}],[{total_cases:4},{total_cases:52}],[{total_cases:68}]];

const result = array.map(e => e.at(-1).total_cases);

console.log(...result);

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

Is there a way to retrieve the final elements from a deeply nested array?

Answer №1

Answer №2

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