const ranges = [
{ from: '01-10-2014', to: '04-10-2014' },
{ from: '05-10-2014', to: '11-10-2014' },
{ from: '12-10-2014', to: '18-10-2014' },
{ from: '19-10-2014', to: '25-10-2014' },
{ from: '26-10-2014', to: '31-10-2014' },
{ from: '01-10-2014', to: '31-10-2014' },
{ from: '09-10-2014', to: '31-10-2014' }
];
for (const range of ranges) {
const dateFormat = 'DD-MM-YYYY';
const diff = Math.abs(moment(range.from, dateFormat).diff(moment(range.to, dateFormat), 'weeks', true));
console.log(diff.toFixed(2));
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.29.1/moment.min.js"></script>