I have a requirement to show modal popup on in netsuite on button click. currently I open a window using client script
var url = nlapiResolveURL('SUITELET','customscript_id','customdeploy_id',null);
window.open(url);
Now I want to make this window as modal popup to prevent accessing the parent window. Please help.
You'll need to use existing solutions like Bootsrap or Jquery UI's Modal Window.
If you want to be more elegant and avoid dependencies, you can create your own light implementation. Please, refer to how to make window.open pop up Modal?