How can I ensure the text stays within the container and doesn't overflow?

[bluebooger]

"I've tried debugging it,"

obviously not very well
just add some console.log statements in there , like this 
and you'll see the problem

Code:

function calculateSum(arr) {
let sum = 0;
for (let i = 0; i <= arr.length; i++) {
  console.log(i + ' = ' + sum);
  sum += arr[i];
}
console.log('sum = ' + sum);
return sum;
}

const numbers = [1, 2, 3, 4, 5];
const result = calculateSum(numbers);
console.log(result); // Output should be 15, but it's not