观鸟者练习 Javascript 解决方案 - 计数器不计数

Question

I'm trying to figure out an exercise from Exercism's Javascript track. It is an exercise using for loops called Bird Watcher.

The instructions say to initialize a function called birdsInWeek that takes two arguments. First is an array 'birdsPerDay', and the second is 'week'. Given the birdsPerDay array, the function is supposed to count the total number of birds seen in the specified week. So, if 'week' = 1, for example, the corresponding indexes of 'birdsPerDay' to add together would be 0 - 6, and so on and so forth.

I have tested my code using the provided test cases and in the Chrome console. I tried logging some values to understand where the bug is, but I can't figure out why my counter (named 'totalBirdsInSpecifiedWeek'), which is initialized to '0' is staying at '0' instead of adding the corresponding indexes of 'week' together and return the correct 'totalBirdsInSpecifiedWeek'. I have tried changing the placement of the return statement as well, but that didn't result in any change.

Below is the code I have written:

export function birdsInWeek(birdsPerDay, week) {
  let totalBirdsInSpecifiedWeek = 0
  if (week === 1) {
    for (let i = 0; i < birdsPerDay[7]; i++) {
      totalBirdsInSpecifiedWeek += birdsPerDay[i];
    } 
    return totalBirdsInSpecifiedWeek;
  } else {
  for (let i = week * 7 - 7; i < birdsPerDay[week * 7]; i++) {
    totalBirdsInSpecifiedWeek += birdsPerDay[i];
  }
  return totalBirdsInSpecifiedWeek;
};
}

Where did I go wrong?

Answer 1

birdsPerDay[7] this means values of birdsPerDay array at index 7 of the array so the condition would loop checking if i is lesser than that value sometimes it would even hit the NaN so the idea is to just check on either length or index of the array to get an accurate response..

Answer 2

Per the commenter @gog, I changed the 4th and 9th lines of code to correct the stopping condition in each of the for loops so they are written as indexes of the 'birdsPerDay' array and instead just numerical values.

export function birdsInWeek(birdsPerDay, week) {
  let totalBirdsInSpecifiedWeek = 0
  if (week === 1) {
    for (let i = 0; i < 7; i++) {
      totalBirdsInSpecifiedWeek += birdsPerDay[i];
    } 
    return totalBirdsInSpecifiedWeek;
  } else {
  for (let i = week * 7 - 7; i < week * 7; i++) {
    totalBirdsInSpecifiedWeek += birdsPerDay[i];
  }
  return totalBirdsInSpecifiedWeek;
}; return totalBirdsInSpecifiedWeek;
}

Answer 3

I found the exercise, according to the problem posed, I think this is the solution. bird-watcher - exercism

Explanation, the array is divided by the days of the week, then the array is divided by that amount from 0 to 6 (Monday to Sunday), then I used a nested "for" to iterate over the corresponding week, I used another "for" to do the addition, return the value from the function and return the result.

let countsbirdsPerDay = [2, 5, 0, 7, 4, 1, 3, 0, 2, 5, 0, 1, 3, 1];
let userWeek = 2;

const birdsInWeek = (birdsPerDay, week) => {
    let segmentWeek = Math.round(birdsPerDay.length / week);
    let total = 0;
    for (let i = 0; i < week; i++) {
        views = birdsPerDay.slice(i * segmentWeek, segmentWeek * (i + 1));
        if ((i + 1) == week) {
            for (let x = 0; x < views.length; x++) {
                total = total + views[x];
            }       
        }
    }
    return total;
}

console.log(birdsInWeek(countsbirdsPerDay, userWeek));