Auto Fill Cell Script - google-apps-script

Question

I have a sheet with two columns. A Date and Assist.
The sheet is filled out with a Date and with a number of how many assist.
What I would like is for the Assist column to automatically insert a 0 if there is a date entered and only if there is no number already in the Assist column.
I have the following script so far and it is triggered onOpen.
function storeValue() {
var ss = SpreadsheetApp.getActiveSpreadsheet();
// ss is now the spreadsheet the script is associated with
var sheet = ss.getSheets()[0]; // sheets are counted starting from 0
// sheet is the first worksheet in the spreadsheet
var cell = sheet.getRange("J3:J");
cell.setValue(0);
}`

Answer 1

This is a little slow, but works. Adapt as needed. It currently assumes your data are in columns A & B.
function storeValue() {
var ss = SpreadsheetApp.getActiveSpreadsheet();
// ss is now the spreadsheet the script is associated with
var sheet = ss.getSheets()[0]; // sheets are counted starting from 0
var dataRange = sheet.getRange("A:B")
for (var row = 1; dataRange.getNumRows(); row++) {
if(sheet.getRange(row,1).getValue() != ''){
if(sheet.getRange(row,2).getValue() == ''){
sheet.getRange(row,2).setValue(0);
}
}
}
}