A possible way of expressing Scheme let expressions, such as

(let ((x 3) (y 5)) (+ x y))

is to use ES6 default parameters:

((x = 3, y = 5) => x + y)()

It is possible to go one step further by defining an auxiliary let_ function as:

const let_ = f => f();  

This allows rewriting the previous function application as:

let_((x = 3, y = 5) => x + y);  

Definitely not the most idiomatic thing to do, though :-)