I recently encountered this problem when referencing FileSaver.js in my project. The code worked in all browsers except Internet Explorer 11.
This post in StackOverflow helped me resolve the problem.
The problem was caused by a meta tag forcing the browser to behave like IE 8.
<meta http-equiv="X-UA-Compatible" content="IE=8"/>
This is an issue as my HTML5 reference is now broken.
A simple change resolved the problem.
<meta http-equiv="X-UA-Compatible" content="IE=edge"/>