RangeError: Maximum call stack size exceeded [Steamroller]

JavaScript
#1

I’m working on a problem is known as Steamroller.
Here is my code to fix this,

function steamrollArray(arr) {
  arr = arr.reduce((acc, val) => acc.concat(val), []);
  var result = [];
  for(let i=0; i<arr.length; i++){
    result.push(typeof(arr[i]));
  }
  for(let i=0; i<result.length; i++){
    if(result[i] === "object"){
      arr = steamrollArray(arr);
    }
  }
  return arr;
}

One of the test cases didn’t pass. It was - steamrollArray([1, {}, [3, [[4]]]]) should return [1, {}, 3, 4]

It’s showing an error - RangeError: Maximum call stack size exceeded
But I don’t understand what is stack or stack size that exceeded?
Can you please explain what’s going on with my code :roll_eyes:

#2

You’ve set up an infinite recursion here.

The ‘call stack’ is a sort of ToDo list of the function calls your computer needs to complete. With an infinite recursion, this stack keeps getting bigger and bigger until JavaScript crashes.

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#3

After all the list of Arr turns to string or number, there will be no object left in Arr. Why it’s infinite?

#4

This isn’t happening though. You are just copying the array.

Three pieces of advice

  • Don’t try to replace arr, build a new array with the ‘unrolled’ contents

  • You only need one loop (and a reduce is a type of loop, in a sense)

  • Recursion needs a reduced input to terminate. What about unrolling entries of arr?

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#5

Is that a good fix? :grimacing:

function steamrollArray(arr) {
  for(let i=0; i<arr.length; i++){
    arr = arr.reduce((acc, val) => acc.concat(val), []);
  }
  return arr;
}
#6

Unfortunately, this solution works by luck with the test suite and won’t work for every single test case.

console.log(steamrollArray([1, [[[[[2]]]]], [3, [[4]]]]))
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