I found it as:
var Firstname = document.getElementsByName("Firstname");
for (var i=0; i < Firstname.length; i++) {
Firstname[i].value = getAllUrlParams().Firstname;
}
I found it as:
var Firstname = document.getElementsByName("Firstname");
for (var i=0; i < Firstname.length; i++) {
Firstname[i].value = getAllUrlParams().Firstname;
}