Hi,
try this method.
var Input = Textfield1.rawValue;
var NameParts = Input.split("\u0020");
if (NameParts.length === 1)
{
FirstName.rawValue = NameParts.slice(0,1).toString();
MiddleName.rawValue = "";
LastName.rawValue = "";
}
if (NameParts.length === 2)
{
FirstName.rawValue = NameParts.slice(0,1).toString();
MiddleName.rawValue = "";
LastName.rawValue = NameParts.slice(1,2).toString();
}
if (NameParts.length === 3)
{
FirstName.rawValue = NameParts.slice(0,1).toString();
MiddleName.rawValue = NameParts.slice(1,2).toString();
LastName.rawValue = NameParts.slice(2,3).toString();
}