Google apps script - Broken for loop

Question

I'm working in Google apps script and seem to have screwed up one of my for loops. I'm sure that I am missing something trivial here, but I can't seem to spot it.

Code Snippet:

var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheets = ss.getSheets();
var lastRow = sheets[3].getLastRow();
var zw = sheets[3].getRange(2, 1, lastRow - 1, 26).getValues();
for (var j = 0; j < zw.length; ++j) {
    if (zw[j][9] === 'Yes') {
        var masterEmail = [];
        var firstLetterLastName = [];
        var first2Letter = [];
        var masterEmail.push(zw[j][22]);
        var firstLetterLastName.push(zw[j][1].charAt(0).toLowerCase());
        var first2Letter.push(zw[j][1].charAt(0).toLowerCase() + zw[j][1].charAt(1).toLowerCase());
        //The rest of the function follows...
    }
}

What's Not Working:

The for loop doesn't increment. When running the code in a debugger, var j stays at a value of 0.0, and the rest of the function only runs based of off the values in the 0 position of zw.

What I need it to do (AKA - How I thought I had written it:)

The ZW variable is holding a 2 dimensional array of cell values from a Google sheet. I'm looping through that, checking the 9th value of each array entry for a string of "Yes" and then running the rest of the function (for each column with a "Yes") if the condition is true.

I thought I had this working before, but recently had to restructure and optimize some things. Now I'm starting to think I may need to rethink things and use a different loop method. Can anyone educate me?

Edit: Here's a bit more context as requested:

function menuItem1() {
  var ui = SpreadsheetApp.getUi();
  var response = ui.alert('Are you sure you want to send emails?', ui.ButtonSet.YES_NO);
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var sheets = ss.getSheets();
  var lastRow = sheets[3].getLastRow();
  var zw = sheets[3].getRange(2, 1, lastRow - 1, 26).getValues();
    if (response === ui.Button.YES) {
      for (var j = 0; j < zw.length; j++) {
        if (zw[j][9] === 'Yes') {
          var firstLetterLastName = [];
          firstLetterLastName.push(zw[j][1].charAt(0).toLowerCase());
          //Other Stuff....
        }
      }
    }
}

I have a menu item attached to a simple onOpen, that calls menuItem1(). Calling the function prompts the user with a warning that they are about to send emails, then goes about getting data to assign email addresses based on the contents of the sheets. firstLetterLastName is an example.

I'm still not getting the loop to function, is it because I have it between two if statements? ( Here is a link to the sheet)

Answer 1

Indeed it is quite trivial. You have mixed up your increment. You wrote

for (var j = 0; j < zw.length; ++j)

which means that you do 1 + i (and we know that at the start i = 0 which means your value will always be 1) instead of using the usual

for (var j = 0; j < zw.length; j++)

which would mean that you do i + 1 and update i , so you will get the expected 0 + 1 1 + 1 etc

EDIT:

First, I recommend instead of something like

if (responseMir === ui.Button.YES) {
  // Your For loop

doing

if (responseMir !== ui.Button.YES) {
  return
}

and in a similar fashion in the for loop

if (zw[j][9] !== 'Yes') {
  break
}

It mostly helps increase readability by not including large blocks of code under a single if, when all you want to do is to stop execution.

Your for loop gets broken because of the mistake here:

teacherEmailMir.push(selValsMir[j][7]);

So your loop will go over once. However on the next itteration, you try to push selValsMir[1][7] which does not exist. Note that each itteration you have var selValsMir = []; inside the loop, which means that for every j selValsMir will always be an empty array. So with the following line

selValsMir.push([zw[j][0], zw[j][1], zw[j][2], zw[j][3], zw[j][4], zw[j][5], zw[j][7], zw[j][22], zw[j][23], zw[j][24]]);

your array will always have selValsMir.lenght = 1 and selValsMir[0].length = 10 . So obviously trying to access anything from selValsMir[1] will throw you an error and stop the script right there.

I also recommend looking over the if statements that look at the first and first 2 letters of the name as I believe you can accomplish the same with less code. Always try to streamline. Consider using switch() where you end up using a lot of else if