Extracting last element of nested array with recursion

Question

I want to flat an array, recursion function calls itself till the last element array but not the last element string, I feel like I am missing something important in understanding how recursion works, the string itself is not added to an empty array.

 const nested = [[[[[['string']]]]], 5, '7']; const funcTest = function (arr) { const final = []; arr.forEach(el => { if (Array.isArray(el)) { console.log(el); funcTest(el); } else final.push(el); }); return final; }; console.log(funcTest(nested));

Answer 1

You can Flattening all nested arrays With flat taking argument depth of Infinity :

    const nested = [[[[[["string"]]]]], 5, "7"];
    nested.flat(Infinity); //['string', 5, '7']

depth: The depth level specifying how deep a nested array structure should be flattened. Defaults to 1.

Answer 2

You need to add the result of the recursive calls.

 const nested = [[[[[['string']]]]], 5, '7']; const funcTest = function (arr) { const final = []; arr.forEach(el => { if (Array.isArray(el)) { console.log(el); final.push(...funcTest(el)); // <- } else final.push(el); }); return final; }; console.log(funcTest(nested));

Another recursive approach:

 const nested = [[[[[['string']]]]], 5, '7']; flatValues = item => Array.isArray(item)? item.flatMap(flatValues): item; console.log(flatValues(nested));

Answer 3

The issue here is that you don't use the return value of the recursive funcTest call.

What you want to do:

const superFlat = (arr) => {
  const result = [];
  
  arr.forEach((item) => {
    if (!Array.isArray(item)) result.push(item);
    else result.push(...superFlat(item));
  });

  return result;
}

Or just use arr.flat(Infinity)