I have added a button to trigger the following JS code to display the versioning history for a list item.

<script type="text/javascript"> var listItem; var list; var title; var clientContext; var item1; var value; var source; var weburl; var currentListGUID;  function getSetListItem() {     source=document.URL;     clientContext = SP.ClientContext.get_current();     if (clientContext != undefined && clientContext != null)     {         weburl=_spPageContextInfo.webServerRelativeUrl;         currentListGUID = SP.ListOperation.Selection.getSelectedList();         if(currentListGUID === "undefined" || currentListGUID === null)         {             alert('Please select one row');         }         else{             var webSite = clientContext.get_web();             var ctx = GetCurrentCtx();             title =ctx.ListTitle;             list = webSite.get_lists().getByTitle(title);             var selectedItems = SP.ListOperation.Selection.getSelectedItems(clientContext);             if(Object.keys(selectedItems).length>1)             {alert('Please select only one row');}             else{                 for (var item in selectedItems)                 {                     item1=selectedItems[item].id;                 }                 listItem = list.getItemById(item1);                 clientContext.load(this.listItem);                 clientContext.executeQueryAsync(Function.createDelegate(this, this.OnLoadSuccess),                 Function.createDelegate(this, this.OnLoadFailed));                 ShowDialog();             }         }     } }  function OnLoadSuccess(sender, args) {     value = this.listItem.get_item("FileLeafRef"); }  function ShowDialog() {     var options =     {         autoSize: true,         allowMaximize: true,         title: 'Version History',         showClose: true,         url:weburl+'/_layouts/15/Versions.aspx?list=' + currentListGUID + '&ID='+item1+'&Source='+weburl+'/Lists/'+title+'/AllItems.aspx',     };     SP.UI.ModalDialog.showModalDialog(options); } </script> 

The code is working well on a SharePoint list page, but what I did is to add the list view webpart to a web part page and then added the button/code. It is strange that the code is working fine when I saved even checked in the page, but it is not working after I published the page. The issue is that, even when I selected an item, when i pushed the button I got the message saying that “Please select one row” as if I didn’t select any rows. the following is the message shown in the console.

Please kindly give me a clue.