Not Able to get the group users using ecmascript

Hi,

I am trying to get the group users on button click,but not able to get so.

Please let me know if I am making any here.

I am getting error message in console as 'groupUsers is not defined'.

<input type="button" id="btnshowusers" value="Show" onclick="ShowUsers()">

function ShowUsers()
{
alert('Entered into Show Users Method')
var clientContext = new SP.ClientContext();
var groupCollection = clientContext.get_web().get_siteGroups();
var oGroup = "groupname";  

var groupUsers = oGroup.get_users();

clientContext.load(groupCollection);
clientContext.load(oGroup);
    clientContext.load(groupUsers);
//alert('after load')
clientContext.executeQueryAsync(Function.createDelegate(this, this.onUserShowSucceeded), Function.createDelegate(this, this.onUserShowFailed)); 
    
    
   /*  this.collUser = oGroup.get_users();
    clientContext.load(collUser); */

}

function onUserShowSucceeded()
{
 
    var userEnumerator = groupUsers.getEnumerator(); 
    while (userEnumerator.moveNext()) {
        var oUser = userEnumerator.get_current();
console.log(oUser.get_id()) ;
}


}function onUserShowFailed(sender, args)
{
alert('Request failed. ' + args.get_message() + '\n' + args.get_stackTrace());
}

Regards,

Naga Sudheer M

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Thanks & Regards, Sudheer