SyntaxError: Invalid shorthand property initializer

Because it is not correct way of assigning value in jQuery-javascript, you need to assign value using : instead of = , So your code should be like this

var i = 1;
$(document).on('click', '.AddMoreaddress', function () {
        $.get('/Mpa/Company/Addreses', { Id=i}, function (data) { // here Id:i instead of Id=i
             i++;
            $("#Addmore").append(data);

         })

})

When assigning values inside {} in javascript, use : instead of =

For example:

This is incorrect

var options = {
  host= 'localhost',
  port= 8080,
 }

This is correct

var options = {
  host: 'localhost',
  port: 8080,
 }

Thanks