Reduce and ternary operator .The ternary operator in reduce method has zero in the 'else' part and return the wrong answer

Question

My reduce function returns 27 instead of 77. I would like to know why this is happening. I AM NOT LOOKING FOR THE SOLUTION. I know the solution, but I don't know why 0 or null in the else portion of my ternary operator doesn't give the correct answer.

const sumFive = arr => arr.reduce((sum, value) => value > 5 ? sum + value : 0, 0)

sumFive([1, 5, 20, 30, 4, 9, 18])

Answer 1

You're resetting the accumulator to 0 every time the iteration comes across a value of 5 or less.

iteration so far --- accumulator returned by iteration

1 --- 0
1, 5 --- 0
1, 5, 20 --- 20
1, 5, 20, 30 --- 50
1, 5, 20, 30, 4 --- 0
1, 5, 20, 30, 4, 9 --- 9
1, 5, 20, 30, 4, 9, 18 --- 27

You need to return the current accumulator value instead of 0 if you want your function to produce the desired output.