[help] update/mutate State on click option

[RanaivosonHerimanitra]

I'm trying to modify a specific book's shelf whenever an option tag is selected:

The above code calls a custom props from a component ListBooks that looks like the following:
<ListBooks onChangeShelf={this.addTo} books ={this.state.books}/>

where addTo is a function which accepts 02 string inputs and is supposed to mutate my state:

Issue: not sure that $set mutates my array according to log
PS: I'm using immutability-helper from npm

Any Hints?
A React Nano Student

[DDDDDanica]

There's an 'update' function in BookAPI to use?

[RanaivosonHerimanitra]

Yeah, solved it ;)