infinite loop occurs when using array.splice inside a for loop

Question

I write this code, for inserting the second argument if any of the array items are bigger than it. but suddenly an infinite loop occurs. ('result.splice(i, 0, num)' causes it) Can anybody tell me why?!

function getIndexToIns(arr, num) {
  let result = arr.sort(function(a, b){return a - b})
  for(let i = 1; i <= result.length ; i++){
    result.splice(i, 0, num)
  }
  return result;
}

getIndexToIns([40, 60, 20, 0], 50);

"if any of the array items are bigger than it" there is nothing in your code that does it. Basically you unconditionally insert new element in array making i <= result.length condition unreachable. — Yury Tarabanko
– Yury Tarabanko, Commented Dec 7, 2020 at 16:03
if you delete count is 0 in splice you are adding to the array instead of replacing. To make your code more maintainable create a new array instead of modifing the existing array. There is a rule of thump to never modify the array you are iterating — c0l3
– c0l3, Commented Dec 7, 2020 at 16:05

Nina Scholz · Accepted Answer · 2020-12-07 16:08:37Z

3

Your

result.splice(i, 0, num)

inserts a new value at the index and increments the length of the array.

Beside that, you loop over the last given index, too.

Instead, you could sort and iterate from the end to replace grater values with the maximum wanted value.

function sortAndReplaceGreaterValues([...array], number) {
    array.sort((a, b) => a - b);
    let i = array.length;
    while (i--) {
        if (array[i] < number) break;
        array[i] = number;
    }
    return array;
}

console.log(sortAndReplaceGreaterValues([40, 60, 20, 0], 50));

answered Dec 7, 2020 at 16:08

Nina Scholz

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