Looping over row and copy them on the next sheet - google-apps-script

Question

I've a list of rows automatically updated and I would like to copy and save them on daily basis.
I've wrote the following script :
function saveData() {
var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheet = ss.getSheets()[0];
var rowcount = sheet.getRange("A1:A").getValues();
var sheetdef = ss.getSheets()[1];
for(var i = 0; i < rowcount.length; i++){
var weeknum = sheet.getRange('Feed!A1').getValue();
var year = sheet.getRange('Feed!B1').getValue();
var date = sheet.getRange('Feed!C1').getValue();
var sessions = sheet.getRange('Feed!D1').getValue();
sheetdef.appendRow([weeknum,year,date,sessions]);
}}
but as you will see it never stop running, plus it only copy the data from the first row. if I'm able to identify my issue I don't really know how to solve it.
I assume that my rowcount line if wrong since it also count blank row. I also need to update sheet.getRange formula so they take dynamic argument.
thanks !

Answer 1

Untested but should work:
function saveData() {
var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheet = ss.getSheets()[0];
//var rowcount = sheet.getRange("A1:A").getValues();
var Avals = ss.getRange("A1:A").getValues();
var rowcount = Avals.filter(String).length; //This will take the last non blank cell from A column
var sheetdef = ss.getSheets()[1];
//I suggest you define Feed sheet as well
var feedsheet = ss.getSheetsByName("Feed")
for(var i = 0; i < rowcount.length; i++){
var weeknum = feedsheet(i,1).getValue(); //<- ith row and first/second column
var year = feedsheet.getRange(i,2).getValue();
var date = feedsheet.getRange(i,3).getValue();
var sessions = feedsheet.getRange(i,4).getValue();
sheetdef.appendRow([weeknum,year,date,sessions]);
}}

Answer 2

With the help of Vasim, I've come up with this:
// function to save data Tendance sessions
function saveData() {
var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheet = ss.getSheets()[0];
var sheetdef = ss.getSheets()[1];
lastRow = sheet.getLastRow();
for (i = lastRow; i > 0; i--){
var weeknum = sheet.getRange(i,1).getValue();
var year = sheet.getRange(i,2).getValue();
var date = sheet.getRange(i,3).getValue();
var sessions = sheet.getRange(i,4).getValue();
sheetdef.appendRow([weeknum,year,date,sessions]);
}}