Simple javaScript to Show a page as modal Dialogbox in SharePoint

Add Content Editor WebPart to Sample.aspx page and add following Code to it

<a href="javascript:var options = {
            url: '/sitepages/Sample.aspx',
            title: 'Title, Description, and Icon',
            width: 640,
            height: 400
        }

        SP.UI.ModalDialog.showModalDialog(options);
;">Show Me the Pop-Up!</a>