Google Sheet Apps Script - Change Cell Data and Increment One Row Down - google-apps-script

Question

I'm trying to.. 1) replace a substring from the contents of the active cell in my sheet, and.. 2) move the active cell down one spot, and repeat until the active cell value is empty. Here's my function, but nothing happens when I run it...can anyone see why?
var app = SpreadsheetApp;
var mySheet = ss.getSheetByName('NAME');
var activeCell = mySheet.getActiveCell();
var cellValue = activeCell.getValue();
var activeRow = activeCell.getRow();
function replaceStringInCell(){
while(cellValue != ''){
var newCellValue = cellValue.replace('MC/Visa/Discover', 'CC');
activeCell.setValue(newCellValue);
activeRow++;
mySheet.getRange(activeRow, 7).activate();
}
}

Answer 1

Issue:
Unnecessary looping over each cell
Solution:
Use batch operations
Sample Script:
function replaceColA() {
var ss = SpreadsheetApp.getActive();
var mySheet = ss.getSheetByName('NAME');
var cellRange = mySheet.getRange('A1:A' + mySheet.getLastRow());
var cellValues = cellRange.getValues().map(replaceStringInCell); //call replace function on all values in range
cellRange.setValues(cellValues); //set mapped values back to range
}
function replaceStringInCell(cellValue) {
if (cellValue.map) {
//if cellValue is a array
return cellValue.map(replaceStringInCell); //recurse
} else {
return cellValue.replace('MC/Visa/Discover', 'CC');
}
}
To Read:
Arrays
Array#Methods
Array#2DFromSpreadsheets
Array#map
String#replace