var city = 'г. Оленегорск, ';
var input = $('.test');
input.focus(function(){
if(input.val() === '') {
input.val('').val(city);
}
});
input.blur(function(){
if (input.val() === city){
input.val('');
}
});
input.on('input change', function(){
var oldValue = input.val();
var newValue = city;
if (oldValue.length > city.length) {
for (var i = city.length; i <= oldValue.length; i++) {
if (typeof oldValue[i] !== 'undefined') {
newValue = newValue + oldValue[i];
}
}
}
input.val(newValue);
});