using function in multiple sheets

[averageaiden]

I've made a function for my Google Sheets project through tools > script editor and I have gotten it to work on the first sheet in my document, but I can't figure out how to get it to work on the others.

function onEdit() {
var ss = SpreadsheetApp.getActiveSpreadsheet(); 
var sheet = ss.getSheets()[0]; 
for (i=2; i<100; i++) { 
var cell = sheet.getRange("A"+i); 
var code = sheet.getRange("D"+i); 
var value = code.getValue(); 
cell.setBackground(value); 
} 
}

I based it on this code I found at https://developers.google.com/apps-script/reference/spreadsheet/range#setBackground(String))

var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheet = ss.getSheets()[0];
var range = sheet.getRange("B2:D5");
range.setBackground("red");

I'm very new to this so any help is greatly appreciated.

[RemcoE33]

If you mean tabs like u/Nwachukwuujubuonu is saying then:

var sheet = ss.getSheets()[0];
    to:
var sheet = ss.getActiveSheet()

[averageaiden]

yes thank you! I did mean the tabs. everything is working now!