How to extract an element of a spreadsheet as a string, not as an array element Google App Script - arrays

Question

(Edited the problem description)
What I am trying to do: Using this Spreadsheet to collect the URLs row by row and paste each image in a new slide of a Google Slide named Output Document. I am using a function addImagetoSlide that takes in the imageUrl, the slide number and the name of the document to add images to each element of the slide.
Where I am stuck When I try to use dataRange (the array containing my spreadsheet element, it works well outside the while loop, but inside the while loop, it does not read the element [0][2] saying that "Cannot read Property 2 of line.. I do not understand why it works outside but not inside the while loop
function collateImages(){
var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheet = ss.getActiveSheet();
var targetDocument = SlidesApp.create("Output Document"); // Target file for the collation
var dataRange = sheet.getDataRange(); // Range of the entire database
Logger.log(dataRange.getValues()[0][2]);
Logger.log(dataRange.getValues()[1][2]);
Logger.log(dataRange.getValues()[2][2]);
Logger.log(dataRange.getValues()[3][2]);
var i = 0; // Iterator
while (i< dataRange.getLastRow()){
i = i + 1;
Logger.log(dataRange.getValues()[i][2]);
addImageToSlide(doubtRange.getValues()[i][2],i,targetDocument);
}
}
// Function to get file id from url
function getIdFromUrl(url) { return url.match(/[-\w]{25,}/); }
//Add Image with URl "ImageUrl" on slide number "index on a presentation named "deck"
function addImageToSlide(imageUrl, index,deck) {
var slide = deck.appendSlide(SlidesApp.PredefinedLayout.BLANK);
var imagefile = DriveApp.getFileById(getIdFromUrl(imageUrl));
var imageblob = imagefile.getBlob();
var image = slide.insertImage(imageblob);
}

Answer 1

The problem with the code you have used is that you are trying to access an index that doesn't exist. As you are incrementing the i value on the last loop, when calling the dataRange.getValues()[i][2], this will try to retrieve the element corresponding to the incremented i which falls out of the range, hence the error message you are receiving.
You can:
move the i increment after calling the dataRange.getValues()[i][2];
use a for loop;
Reference
Sheet Class Apps Script - getDataRange().