Why does IE throw an error in function parameters and when creating an object?

Question

JavaScript

There are 2 moments in the code that IE swears at.
First:
var fn = function(a, b = 50) {};
And second:

var a = 5, b = 3;
var data = {a, b};

In the first case, it waits for ')' right after the variable b, in the second case it complains about the comma after the 'a' object.
Why is this happening and how then to be in this case?

Answer 1

This is the syntactic sugar of es6 and here is its support:
https://kangax.github.io/compat-table/es6/
"how then to be in this case?"
https://babeljs.io