When defining the index of arrays using a loop, the function will return NaN

Question

When defining the index of arrays using a loop, the function will return NaN

I encountered a problem with my project where this function is returning NaN. In the past, I was able to resolve a similar issue by setting a variable equal to 0. However, that solution is not working in this case.

var distanceArray = [
  [0, 62.3, 58.8, 44.6, 33.2],
  [62.3, 0, 37.9, 65.3, 60.1],
  [58.8, 37.9, 0, 40.5, 78.5],
  [44.6, 65.3, 40.5, 0, 77.6],
  [33.2, 60.1, 78.5, 77.6, 0]
]

var route = [0, 1];

function routeFunction() {
  var totalDistance = 0;
  for (var i = 0; i < route.length; i++) {
    totalDistance += distanceArray[route[i]][route[i + 1]];
  }
  return totalDistance;
}

console.log(routeFunction());

javascript arrays function

Answer 1

Answer №1

Your loop begins like this:

for (let count = 0; count < journey.length; count++)

This indicates that the variable count will range from 0 to journey.length - 1, including both values.

Within the loop, you have the following line of code:

x += distanceArray[journey[count]][journey[count + 1]];

Note specifically the journey[count + 1] part. Since count iterates from 0 to journey.length - 1, count + 1 will vary between 1 and journey.length. Therefore, on the last cycle, you are trying to access journey[journey.length]. This index is out of bounds and will result in undefined.

Consequently, you are essentially calculating

distanceArray[journey[count]][undefined]

which evaluates to undefined. The += operator then coerces this into a Number, leading to the appearance of NaN.

To address this issue, adjust the loop condition so it does not attempt to access elements beyond the array's end. Update the loop header to read as follows:

for (let count = 0; count < journey.length - 1; count++)

Answer 2

Your loop begins like this:

for (let count = 0; count < journey.length; count++)

This indicates that the variable count will range from 0 to journey.length - 1, including both values.

Within the loop, you have the following line of code:

x += distanceArray[journey[count]][journey[count + 1]];

Note specifically the journey[count + 1] part. Since count iterates from 0 to journey.length - 1, count + 1 will vary between 1 and journey.length. Therefore, on the last cycle, you are trying to access journey[journey.length]. This index is out of bounds and will result in undefined.

Consequently, you are essentially calculating

distanceArray[journey[count]][undefined]

which evaluates to undefined. The += operator then coerces this into a Number, leading to the appearance of NaN.

To address this issue, adjust the loop condition so it does not attempt to access elements beyond the array's end. Update the loop header to read as follows:

for (let count = 0; count < journey.length - 1; count++)

Answer 3

Answer №2

The issue arises when

z+= avstandArray[reiserute[i]][reiserute[i+1]];

In the code above, there is an attempt to retrieve a value from the reiserute array at the (n+1)th element, which is undefined. Adding this undefined element to a number will result in a NaN exception. Therefore, it is necessary to adjust the logic.

for (var i = 0; i < reiserute.length; i++) {
if(i!=reiserute.length)
    z+= avstandArray[reiserute[i]][reiserute[i+1]];
else
    z+= avstandArray[reiserute[i]];
}

Answer 4

The issue arises when

z+= avstandArray[reiserute[i]][reiserute[i+1]];

In the code above, there is an attempt to retrieve a value from the reiserute array at the (n+1)th element, which is undefined. Adding this undefined element to a number will result in a NaN exception. Therefore, it is necessary to adjust the logic.

for (var i = 0; i < reiserute.length; i++) {
if(i!=reiserute.length)
    z+= avstandArray[reiserute[i]][reiserute[i+1]];
else
    z+= avstandArray[reiserute[i]];
}

Answer 5

Answer №3

It seems like the goal here is unclear, but the main issue at hand is as follows:

The variable "reiserute" does not contain any values and is essentially an empty array. Trying to access values at different indexes within this empty array will result in JavaScript returning "undefined".

reiserute[i] ----> undefined

By attempting to find a value using reiserute[i], you are essentially looking for an undefined value. When trying to access a value in an array by index, JavaScript expects that index to be an integer. Since the index evaluates to undefined, JavaScript throws a NaN error - which stands for "NotANumber".

In this case, the output shows as "0" because the array has a length of zero, causing the condition in the first check to fail and preventing the loop from executing.

If the loop were to execute, it would result in an error displaying NaN.

Answer 6

It seems like the goal here is unclear, but the main issue at hand is as follows:

The variable "reiserute" does not contain any values and is essentially an empty array. Trying to access values at different indexes within this empty array will result in JavaScript returning "undefined".

reiserute[i] ----> undefined

By attempting to find a value using reiserute[i], you are essentially looking for an undefined value. When trying to access a value in an array by index, JavaScript expects that index to be an integer. Since the index evaluates to undefined, JavaScript throws a NaN error - which stands for "NotANumber".

In this case, the output shows as "0" because the array has a length of zero, causing the condition in the first check to fail and preventing the loop from executing.

If the loop were to execute, it would result in an error displaying NaN.

Answer 7

Answer №4

No errors here, the result is simply 0. Due to the initial declaration of var reiserute = [];, the for loop does not iterate at all.

var avstandArray = [
[0, 62.3, 58.8, 44.6, 33.2],
[62.3, 0, 37.9, 65.3, 60.1],
[58.8, 37.9, 0, 40.5, 78.5],
[44.6, 65.3, 40.5, 0, 77.6],
[33.2, 60.1, 78.5, 77.6, 0]
]

var reiserute = [0,1];

function ruteFunction(){
var z = 0;
for (var i = 0; i < reiserute.length; i++) {
    z+= avstandArray[reiserute[i]][reiserute[i+1]];
    console.log(z);
}
return z;
}

console.log(ruteFunction());

Answer 8

No errors here, the result is simply 0. Due to the initial declaration of var reiserute = [];, the for loop does not iterate at all.

var avstandArray = [
[0, 62.3, 58.8, 44.6, 33.2],
[62.3, 0, 37.9, 65.3, 60.1],
[58.8, 37.9, 0, 40.5, 78.5],
[44.6, 65.3, 40.5, 0, 77.6],
[33.2, 60.1, 78.5, 77.6, 0]
]

var reiserute = [0,1];

function ruteFunction(){
var z = 0;
for (var i = 0; i < reiserute.length; i++) {
    z+= avstandArray[reiserute[i]][reiserute[i+1]];
    console.log(z);
}
return z;
}

console.log(ruteFunction());

When defining the index of arrays using a loop, the function will return NaN

Answer №1

Answer №2

Answer №3

Answer №4

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