unable to get property 'createRange' of undefined or null reference

[riksof-zzlalani]

File: TextboxList.js
Line# 411

var r = document.selection.createRange().duplicate();

I'm getting this error only in IE11

unable to get property 'createRange' of undefined or null reference

Since IE 11 has ended the support for the function document.selection

it says

[selection is no longer supported. Starting with Internet Explorer 11, use getSelection. For info, see Compatibility changes.]