Two ways to determine whether a text box is empty in js_javascript skills

//Username non-null verification
function checkUserName(){
var name = document.myform.txtUser; //Here I think: name represents the text box whose name is txtUser
if(name.value.length==0){
alert("Please Enter username");
name.focus();
return false;
}else{return true;}
}
//Password non-empty verification confirmation verification
function checkPass(){
var pass=document.myform.txtPass;
var rpass=document.myform.txtRPass;
if(pass.value==""){
alert("Password cannot be used is empty");
pass.focus();
return false;
}else if (pass.value.length<4 || pass.value.length>16){
alert( "The length of the password must be 4-16 characters");
pass.select();
return false;
}else if(rpass.value!=pass.value){
alert ("The confirmation password is inconsistent with the password input");
rpass.select();
return false;
}else{return true;}
}