javascript – letting users create object themselves (prototype pollution)

Let’s say if there’s some object and an array

let a = [];
let b= {
"c": e // e is user controlled where user inputs get parsed via JSON.parse

a[f] = b // f is user controlled and it is achieved as a string

will the user be able to somehow change the object value in d using the parsed object of c?

And could there be a possible prototype pollution here?

Thank you.