no-const-let.js

function main() {
    const fn1 = a => ({
       get: () => a,
       set: () => {a = 'Good bye!'}
     })

    const a = 'hello'
    const {get, set} = fn1(a)


    // get() holds a reference to a mutable variable
    console.log(get())

    // and because this reference can be mutated
    set()

    // get() is not a pure function now.
    console.log(get())
    console.log(a)
}

main()