Javascript: Loop Through Two Arrays and Sum Elements in Array Via Function

Question

I have the following problem:

Suzuki is a monk who climbs a large staircase to the monastery as part of a ritual. Some days he climbs more stairs than others depending on the number of students he must train in the morning. He is curious how many stairs might be climbed over the next 20 years and has spent a year marking down his daily progress.

The sum of all the stairs logged in a year will be used for estimating the number he might climb in 20.

20_year_estimate = one_year_total * 20

To solve the above problem I tried the following code:

function stairsIn20 (stairs) {

  //console.log(stairs)
  let sum = 0; 

  for (let i=0; i<stairs.length; i++){
    let element = stairs[i]
    //console.log(element)

    for (let j=0; j<element.length; j++){
      //console.log(element[j])

      sum += element[j]
    }  
  return sum
  }
}

var sunday = [6737, 7244, 5776, 9826, 7057, 9247, 5842, 5484, 6543, 5153, 6832, 8274,
          7148, 6152, 5940, 8040, 9174, 7555, 7682, 5252, 8793, 8837, 7320, 8478, 6063, 
          5751, 9716, 5085, 7315, 7859, 6628, 5425, 6331, 7097, 6249, 8381, 5936, 8496, 
          6934, 8347, 7036, 6421, 6510, 5821, 8602, 5312, 7836, 8032, 9871, 5990, 6309, 7825],

monday = [9175, 7883, 7596, 8635, 9274, 9675, 5603, 6863, 6442, 9500, 7468, 9719,
          6648, 8180, 7944, 5190, 6209, 7175, 5984, 9737, 5548, 6803, 9254, 5932, 7360, 9221, 
          5702, 5252, 7041, 7287, 5185, 9139, 7187, 8855, 9310, 9105, 9769, 9679, 7842,
          7466, 7321, 6785, 8770, 8108, 7985, 5186, 9021, 9098, 6099, 5828, 7217, 9387],

tuesday = [8646, 6945, 6364, 9563, 5627, 5068, 9157, 9439, 5681, 8674, 6379, 8292,
           7552, 5370, 7579, 9851, 8520, 5881, 7138, 7890, 6016, 5630, 5985, 9758, 8415, 7313,
           7761, 9853, 7937, 9268, 7888, 6589, 9366, 9867, 5093, 6684, 8793, 8116, 8493, 
           5265, 5815, 7191, 9515, 7825, 9508, 6878, 7180, 8756, 5717, 7555, 9447, 7703],
wednesday = [6353, 9605, 5464, 9752, 9915, 7446, 9419, 6520, 7438, 6512, 7102, 
             5047, 6601, 8303, 9118, 5093, 8463, 7116, 7378, 9738, 9998, 7125, 6445, 6031, 8710,
             5182, 9142, 9415, 9710, 7342, 9425, 7927, 9030, 7742, 8394, 9652, 5783, 7698, 
             9492, 6973, 6531, 7698, 8994, 8058, 6406, 5738, 7500, 8357, 7378, 9598, 5405, 9493],
thursday = [6149, 6439, 9899, 5897, 8589, 7627, 6348, 9625, 9490, 5502, 5723, 8197,
            9866, 6609, 6308, 7163, 9726, 7222, 7549, 6203, 5876, 8836, 6442, 6752, 8695, 8402,
            9638, 9925, 5508, 8636, 5226, 9941, 8936, 5047, 6445, 8063, 6083, 7383, 7548, 5066, 
            7107, 6911, 9302, 5202, 7487, 5593, 8620, 8858, 5360, 6638, 8012, 8701],
friday = [5000, 5642, 9143, 7731, 8477, 8000, 7411, 8813, 8288, 5637, 6244, 6589, 6362, 
         6200, 6781, 8371, 7082, 5348, 8842, 9513, 5896, 6628, 8164, 8473, 5663, 9501, 
         9177, 8384, 8229, 8781, 9160, 6955, 9407, 7443, 8934, 8072, 8942, 6859, 5617,
         5078, 8910, 6732, 9848, 8951, 9407, 6699, 9842, 7455, 8720, 5725, 6960, 5127],
saturday = [5448, 8041, 6573, 8104, 6208, 5912, 7927, 8909, 7000, 5059, 6412, 6354, 8943, 
            5460, 9979, 5379, 8501, 6831, 7022, 7575, 5828, 5354, 5115, 9625, 7795, 7003, 
            5524, 9870, 6591, 8616, 5163, 6656, 8150, 8826, 6875, 5242, 9585, 9649, 9838, 
            7150, 6567, 8524, 7613, 7809, 5562, 7799, 7179, 5184, 7960, 9455, 5633, 9085];

var stairs = [sunday,monday,tuesday,wednesday,thursday,friday,saturday]


stairsIn20(stairs)

The above code produces the following output: 371,564 which is wrong. The correct answer appears to be 2,731,802. What is wrong with my code?

Answer 1

You can use following function to calulate sum.

function stairsIn20 (stairs) 
{ 
    let sum = 0; 
    stairs.forEach(function(item,index)
    { 
        item.forEach(function(item1,index1)
        {
          sum=sum+item1;
         }) 
    })
    return sum
}

Answer 2

Try a reduce function.

function stairsIn20 (stairs) {
  return stairs.reduce((accum, curr) => {
    return accum + curr;
  }, 0);
}

const sunday = [6737, 7244, 5776, 9826, 7057, 9247, 5842, 5484, 6543, 5153, 6832, 8274,
          7148, 6152, 5940, 8040, 9174, 7555, 7682, 5252, 8793, 8837, 7320, 8478, 6063, 
          5751, 9716, 5085, 7315, 7859, 6628, 5425, 6331, 7097, 6249, 8381, 5936, 8496, 
          6934, 8347, 7036, 6421, 6510, 5821, 8602, 5312, 7836, 8032, 9871, 5990, 6309, 7825],

monday = [9175, 7883, 7596, 8635, 9274, 9675, 5603, 6863, 6442, 9500, 7468, 9719,
          6648, 8180, 7944, 5190, 6209, 7175, 5984, 9737, 5548, 6803, 9254, 5932, 7360, 9221, 
          5702, 5252, 7041, 7287, 5185, 9139, 7187, 8855, 9310, 9105, 9769, 9679, 7842,
          7466, 7321, 6785, 8770, 8108, 7985, 5186, 9021, 9098, 6099, 5828, 7217, 9387],

tuesday = [8646, 6945, 6364, 9563, 5627, 5068, 9157, 9439, 5681, 8674, 6379, 8292,
           7552, 5370, 7579, 9851, 8520, 5881, 7138, 7890, 6016, 5630, 5985, 9758, 8415, 7313,
           7761, 9853, 7937, 9268, 7888, 6589, 9366, 9867, 5093, 6684, 8793, 8116, 8493, 
           5265, 5815, 7191, 9515, 7825, 9508, 6878, 7180, 8756, 5717, 7555, 9447, 7703],
wednesday = [6353, 9605, 5464, 9752, 9915, 7446, 9419, 6520, 7438, 6512, 7102, 
             5047, 6601, 8303, 9118, 5093, 8463, 7116, 7378, 9738, 9998, 7125, 6445, 6031, 8710,
             5182, 9142, 9415, 9710, 7342, 9425, 7927, 9030, 7742, 8394, 9652, 5783, 7698, 
             9492, 6973, 6531, 7698, 8994, 8058, 6406, 5738, 7500, 8357, 7378, 9598, 5405, 9493],
thursday = [6149, 6439, 9899, 5897, 8589, 7627, 6348, 9625, 9490, 5502, 5723, 8197,
            9866, 6609, 6308, 7163, 9726, 7222, 7549, 6203, 5876, 8836, 6442, 6752, 8695, 8402,
            9638, 9925, 5508, 8636, 5226, 9941, 8936, 5047, 6445, 8063, 6083, 7383, 7548, 5066, 
            7107, 6911, 9302, 5202, 7487, 5593, 8620, 8858, 5360, 6638, 8012, 8701],
friday = [5000, 5642, 9143, 7731, 8477, 8000, 7411, 8813, 8288, 5637, 6244, 6589, 6362, 
         6200, 6781, 8371, 7082, 5348, 8842, 9513, 5896, 6628, 8164, 8473, 5663, 9501, 
         9177, 8384, 8229, 8781, 9160, 6955, 9407, 7443, 8934, 8072, 8942, 6859, 5617,
         5078, 8910, 6732, 9848, 8951, 9407, 6699, 9842, 7455, 8720, 5725, 6960, 5127],
saturday = [5448, 8041, 6573, 8104, 6208, 5912, 7927, 8909, 7000, 5059, 6412, 6354, 8943, 
            5460, 9979, 5379, 8501, 6831, 7022, 7575, 5828, 5354, 5115, 9625, 7795, 7003, 
            5524, 9870, 6591, 8616, 5163, 6656, 8150, 8826, 6875, 5242, 9585, 9649, 9838, 
            7150, 6567, 8524, 7613, 7809, 5562, 7799, 7179, 5184, 7960, 9455, 5633, 9085];

const stairs = sunday.concat(monday,tuesday,wednesday,thursday,friday,saturday)



console.log(stairsIn20(stairs));

Answer 3

You need to move the return statement below of the for loop, right before the function ends.

function stairsIn20(stairs) {
    let sum = 0;
    for (let i = 0; i < stairs.length; i++) {
        let element = stairs[i]
        for (let j = 0; j < element.length; j++) {
            sum += element[j]
        }
    }
    return sum; // move to the end
}

var sunday = [6737, 7244, 5776, 9826, 7057, 9247, 5842, 5484, 6543, 5153, 6832, 8274, 7148, 6152, 5940, 8040, 9174, 7555, 7682, 5252, 8793, 8837, 7320, 8478, 6063, 5751, 9716, 5085, 7315, 7859, 6628, 5425, 6331, 7097, 6249, 8381, 5936, 8496, 6934, 8347, 7036, 6421, 6510, 5821, 8602, 5312, 7836, 8032, 9871, 5990, 6309, 7825],
    monday = [9175, 7883, 7596, 8635, 9274, 9675, 5603, 6863, 6442, 9500, 7468, 9719, 6648, 8180, 7944, 5190, 6209, 7175, 5984, 9737, 5548, 6803, 9254, 5932, 7360, 9221, 5702, 5252, 7041, 7287, 5185, 9139, 7187, 8855, 9310, 9105, 9769, 9679, 7842, 7466, 7321, 6785, 8770, 8108, 7985, 5186, 9021, 9098, 6099, 5828, 7217, 9387],
    tuesday = [8646, 6945, 6364, 9563, 5627, 5068, 9157, 9439, 5681, 8674, 6379, 8292, 7552, 5370, 7579, 9851, 8520, 5881, 7138, 7890, 6016, 5630, 5985, 9758, 8415, 7313, 7761, 9853, 7937, 9268, 7888, 6589, 9366, 9867, 5093, 6684, 8793, 8116, 8493, 5265, 5815, 7191, 9515, 7825, 9508, 6878, 7180, 8756, 5717, 7555, 9447, 7703],
    wednesday = [6353, 9605, 5464, 9752, 9915, 7446, 9419, 6520, 7438, 6512, 7102, 5047, 6601, 8303, 9118, 5093, 8463, 7116, 7378, 9738, 9998, 7125, 6445, 6031, 8710, 5182, 9142, 9415, 9710, 7342, 9425, 7927, 9030, 7742, 8394, 9652, 5783, 7698, 9492, 6973, 6531, 7698, 8994, 8058, 6406, 5738, 7500, 8357, 7378, 9598, 5405, 9493],
    thursday = [6149, 6439, 9899, 5897, 8589, 7627, 6348, 9625, 9490, 5502, 5723, 8197, 9866, 6609, 6308, 7163, 9726, 7222, 7549, 6203, 5876, 8836, 6442, 6752, 8695, 8402, 9638, 9925, 5508, 8636, 5226, 9941, 8936, 5047, 6445, 8063, 6083, 7383, 7548, 5066, 7107, 6911, 9302, 5202, 7487, 5593, 8620, 8858, 5360, 6638, 8012, 8701],
    friday = [5000, 5642, 9143, 7731, 8477, 8000, 7411, 8813, 8288, 5637, 6244, 6589, 6362, 6200, 6781, 8371, 7082, 5348, 8842, 9513, 5896, 6628, 8164, 8473, 5663, 9501, 9177, 8384, 8229, 8781, 9160, 6955, 9407, 7443, 8934, 8072, 8942, 6859, 5617, 5078, 8910, 6732, 9848, 8951, 9407, 6699, 9842, 7455, 8720, 5725, 6960, 5127],
    saturday = [5448, 8041, 6573, 8104, 6208, 5912, 7927, 8909, 7000, 5059, 6412, 6354, 8943, 5460, 9979, 5379, 8501, 6831, 7022, 7575, 5828, 5354, 5115, 9625, 7795, 7003, 5524, 9870, 6591, 8616, 5163, 6656, 8150, 8826, 6875, 5242, 9585, 9649, 9838, 7150, 6567, 8524, 7613, 7809, 5562, 7799, 7179, 5184, 7960, 9455, 5633, 9085],
    stairs = [sunday, monday, tuesday, wednesday, thursday, friday, saturday];

console.log(stairsIn20(stairs));