What is the most efficient way to retrieve an index within a recursive function in JavaScript?

Question

What is the most efficient way to retrieve an index within a recursive function in JavaScript?

let array = [1, [2, 3, [4, 5, ["six", "seven", 6666, [8, 9, [10]]]]]]
    //1. Identify and access the last element
   //2. Utilize index notation like in **console.log(array[1][2][2][3][2][0]** but should output 
  // [1][2][2][3][2][0] or 1,2,2,3,2,0

Within this function, I have successfully located the last element but now I am struggling to locate the second question (which requires a recursive function)

function findLastElement(arr){
       for (let element of arr ){
          if(typeof element === "object"){
             findLastElement(element)
              console.log(element)
          }
       }
}

findLastElement(array)

javascript arrays function object recursion

Answer 1

Answer №1

If you want to retrieve all the indexes that are less than the last index in an array, you can achieve this by using a recursive function that checks if the last item is also an array:

const getLessIndexes = arr => {
  const last = arr.length - 1
  
  return [
    last,
    ...Array.isArray(arr[last]) 
      ? getLessIndexes(arr[last]) 
      : []
  ]
}

const array = [1, [2, 3, [4, 5, ["six", "seven", 6666, [8, 9, [10]]]]]]

const result = getLessIndexes(array)

console.log(result)

Answer 2

If you want to retrieve all the indexes that are less than the last index in an array, you can achieve this by using a recursive function that checks if the last item is also an array:

const getLessIndexes = arr => {
  const last = arr.length - 1
  
  return [
    last,
    ...Array.isArray(arr[last]) 
      ? getLessIndexes(arr[last]) 
      : []
  ]
}

const array = [1, [2, 3, [4, 5, ["six", "seven", 6666, [8, 9, [10]]]]]]

const result = getLessIndexes(array)

console.log(result)

Answer 3

Answer №2

If you want to iterate through an array and get both the index and element, you can use the Array.entries() method.

function findLastObj (arr){
  for (let [index, obj] of arr.entries() ){
    if(typeof obj === "object"){
      findLastObj(obj)
      console.log(obj)
      console.log(index)
    }
  }
}

Answer 4

If you want to iterate through an array and get both the index and element, you can use the Array.entries() method.

function findLastObj (arr){
  for (let [index, obj] of arr.entries() ){
    if(typeof obj === "object"){
      findLastObj(obj)
      console.log(obj)
      console.log(index)
    }
  }
}

Answer 5

Answer №3

let numbers = [1, [2, 3, [4, 5, ["six", "seven", 6666, [8, 9, [10]]]]]];

function findLastValue (arr){
  for (let [position, item] of arr.entries() ){
    if(typeof item === "object"){
      findLastValue(item)
      console.log(item)
      console.log(position)
    }
  }
}

console.log( findLastValue(numbers) )

Answer 6

let numbers = [1, [2, 3, [4, 5, ["six", "seven", 6666, [8, 9, [10]]]]]];

function findLastValue (arr){
  for (let [position, item] of arr.entries() ){
    if(typeof item === "object"){
      findLastValue(item)
      console.log(item)
      console.log(position)
    }
  }
}

console.log( findLastValue(numbers) )

What is the most efficient way to retrieve an index within a recursive function in JavaScript?

Answer №1

Answer №2

Answer №3

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