According to this page http://kangax.github.io/compat-table/es6/, ES6 features are not implemented in IE 11.
Does IE 11 have a plan for implementing them one day or
The statement from Microsoft regarding the end of Internet Explorer 11 support mentions that it will continue to receive security updates, compatibility fixes, and technical support until its end of life. The wording of this statement leads me to believe that Microsoft has no plans to continue adding features to Internet Explorer 11, and instead will be focusing on Edge.
If you require ES6 features in Internet Explorer 11, check out a transpiler such as Babel.