What is the optimal way to update an array within a loop only when a certain condition is met?

Question

What is the optimal way to update an array within a loop only when a certain condition is met?

I am currently working on a function that will iterate through folders in Google Drive, searching for files (Google Sheets) that match a specific date specified in a table cell. Once a matching file is found, the name of the containing folder is stored in the folderItems[0] and the file's URL is stored in folderItems[1]. The process continues until all matching files within a folder have been identified, after which it moves on to the next folder. These folderItem arrays are then collected in a parent array called "folderItemsContainer," creating a 2-dimensional array that can be easily outputted to a spreadsheet using .setValues().

My main challenge right now is determining the best placement for an increment variable. I need it to only increment when a filename match is found, without causing the loop to stop if no match is detected.

I have experimented with different structures, including switching between for and while loops and adding if statements at strategic points. I've also researched various answers on Stackoverflow, but none seem to directly apply to my situation. As someone who is relatively new to programming, I have tried multiple variations of code, but here is where I stand currently:

 // Your function code goes here...

Despite my efforts, the script seems to get stuck in an endless loop and never completes. My goal is to populate the folderItemsContainer array with arrays containing the necessary file information (parent folder name [0] and file URL [1]) for files that match the currentYearPeriod variable. Although I have made progress in refactoring the code, I have yet to find a solution to this issue.

javascript arrays google-apps-script

Answer 1

Answer №1

It's important to understand the difference between each type of loop in programming. If you need to execute a set of instructions until a certain condition is met, like

file.getName().indexOf(currentYearPeriod) !== -1

, then a while loop would be more suitable than a for loop. The issue with your code is that the condition in the for loop is never met because the variable file doesn't change within the loop, leading to an infinite loop. Here is a suggested solution:

// declare a new variable
var cnt = 0;

while (StaffFolders.hasNext()) {
    currentFolder = StaffFolders.next();
    FolderFiles = currentFolder.getFiles();

    if (FolderFiles !== null) {
      while (FolderFiles.hasNext()) {
        file = FolderFiles.next();

        folderItems[cnt] = [];
        folderItems[cnt][0] = currentFolder.getName();
        folderItems[cnt][1] = file.getUrl();
        folderItemsContainer[cnt] = folderItems[cnt];

        cnt++;
      }
    }
    cnt = 0;
  }

Differences between loops:

for loops

For loops are used when the number of iterations is known beforehand. For example, printing each character of a string in the console:

const str = "hello";
for(let i = 0; i < str.length; i++) {
   console.log(str.charAt(i));
}

let i = 0 initializes the loop
i < str.length defines the end condition
i++ specifies how to iterate through the loop

while loops

While loops are ideal when the number of iterations is uncertain. For instance, searching for the index of a specific character in a string:

function getFirstL(str)
   let i = 0;
   while(i < str.length && str.charAt(i) !== "l"){
      i++;
   }
}

Answer 2

It's important to understand the difference between each type of loop in programming. If you need to execute a set of instructions until a certain condition is met, like

file.getName().indexOf(currentYearPeriod) !== -1

, then a while loop would be more suitable than a for loop. The issue with your code is that the condition in the for loop is never met because the variable file doesn't change within the loop, leading to an infinite loop. Here is a suggested solution:

// declare a new variable
var cnt = 0;

while (StaffFolders.hasNext()) {
    currentFolder = StaffFolders.next();
    FolderFiles = currentFolder.getFiles();

    if (FolderFiles !== null) {
      while (FolderFiles.hasNext()) {
        file = FolderFiles.next();

        folderItems[cnt] = [];
        folderItems[cnt][0] = currentFolder.getName();
        folderItems[cnt][1] = file.getUrl();
        folderItemsContainer[cnt] = folderItems[cnt];

        cnt++;
      }
    }
    cnt = 0;
  }

Differences between loops:

for loops

For loops are used when the number of iterations is known beforehand. For example, printing each character of a string in the console:

const str = "hello";
for(let i = 0; i < str.length; i++) {
   console.log(str.charAt(i));
}

let i = 0 initializes the loop
i < str.length defines the end condition
i++ specifies how to iterate through the loop

while loops

While loops are ideal when the number of iterations is uncertain. For instance, searching for the index of a specific character in a string:

function getFirstL(str)
   let i = 0;
   while(i < str.length && str.charAt(i) !== "l"){
      i++;
   }
}

Answer 3

Answer №2

Understanding the concept of a for loop is crucial in programming.

for (initialization; condition; increment/decrement) {
  // code to be iterated
}

The initialization statement runs once before entering the loop.

The condition decides whether to execute the loop or not.

The increment/decrement statement runs after each iteration of the loop.

Your current for loop lacks an exit condition, such as a minimum or maximum value check like:

i < file.getName().indexOf(currentYearPeriod);

This means the loop will iterate from 0 up to that specified value.

Answer 4

Understanding the concept of a for loop is crucial in programming.

for (initialization; condition; increment/decrement) {
  // code to be iterated
}

The initialization statement runs once before entering the loop.

The condition decides whether to execute the loop or not.

The increment/decrement statement runs after each iteration of the loop.

Your current for loop lacks an exit condition, such as a minimum or maximum value check like:

i < file.getName().indexOf(currentYearPeriod);

This means the loop will iterate from 0 up to that specified value.

What is the optimal way to update an array within a loop only when a certain condition is met?

Answer №1

Answer №2

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