jMarshal
Mega Sage

Try an intermediate variable perhaps? I'm thinking it's not actually storing the value in the variable after the prompt.

var FirstName;
var LastName;
var FullName;

 

function ChangeName() {
    FirstName = prompt("Enter Firstname");
    LastName = prompt("Enter Lastname");
    if (FirstName && LastName) {
        alert('Name captured is ' + FirstName + " " + LastName);
FullName = FristName + " " + LastName;
alert('Full name is ' + FullName);
    }
    gsftSubmit(null, g_form.getFormElement(), "user_change_name");
}

 

if (typeof window == 'undefined')
    updateItem();

 

function updateItem() {
    var gr = new GlideRecord('sc_req_item');
    gr.initialize();
    gr.assignment_group = '4a1d990547056510d2c3b604836d432e'// ServiceNow admin team
    gr.description = 'Change the name to: ' + FullName;
    gr.insert();
    action.setRedirectURL(current);
}