JavaScript Not Correctly Flattening Array within Function

Question

JavaScript Not Correctly Flattening Array within Function

I have been working on a JavaScript function to flatten a nested array, but I'm encountering a problem. The function only returns the original array instead of flattening it. For example, when I run the function with the array [1, 2, 3, [4, 5, [6], []]], it simply outputs the same array. Even though I am using the .map method and recursion to manipulate the return values, it's not functioning as expected.

function mapper(array) { 
    return array.map((item) => {
        return (Array.isArray(item)) ? mapper(item) : item
    } 
)}

javascript arrays nested

Answer 1

Answer №1

What is the underlying reason that prevents this particular approach from functioning as expected?

 var arr = [1, 2, 3, [4, 5, [6], []]];
 function applyMapping(array) { 
        return array.map((item) => {
            // For elements 1, 2, 3 it will simply return the item
            // When encountering another array, it will recursively call the mapping function
            // The function will generate a new array, so mapping over 
            // [4, 5, [6], []] will create a new array without extracting 
            // individual elements and appending them to the previous array

            return (Array.isArray(item)) ? applyMapping(item) : item
        } 
    )}
applyMapping(arr)

The map function does not modify the original array but rather produces a new array.

Answer 2

What is the underlying reason that prevents this particular approach from functioning as expected?

 var arr = [1, 2, 3, [4, 5, [6], []]];
 function applyMapping(array) { 
        return array.map((item) => {
            // For elements 1, 2, 3 it will simply return the item
            // When encountering another array, it will recursively call the mapping function
            // The function will generate a new array, so mapping over 
            // [4, 5, [6], []] will create a new array without extracting 
            // individual elements and appending them to the previous array

            return (Array.isArray(item)) ? applyMapping(item) : item
        } 
    )}
applyMapping(arr)

The map function does not modify the original array but rather produces a new array.

Answer 3

Answer №2

When you map the array to itself, what happens is that it will always return an array with the same number of elements as the input. This means that you cannot expect it to bring back more elements, making it unsuitable for flattening the array.

A better solution would be to utilize the reduce method instead:

 function flattenArray(arr) {

     if (Array.isArray(arr)) {
          return arr.reduce((prev, curr) => prev.concat(flattenArray(curr)), []);
     } else {
          return [arr];
     }
 }

Answer 4

When you map the array to itself, what happens is that it will always return an array with the same number of elements as the input. This means that you cannot expect it to bring back more elements, making it unsuitable for flattening the array.

A better solution would be to utilize the reduce method instead:

 function flattenArray(arr) {

     if (Array.isArray(arr)) {
          return arr.reduce((prev, curr) => prev.concat(flattenArray(curr)), []);
     } else {
          return [arr];
     }
 }

JavaScript Not Correctly Flattening Array within Function

Answer №1

Answer №2

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