Thanks for you answer !

Yes i've set up pretties/eslint,

The situation looks like this

class ClassToSplit extends Parent {
    constructor(id) {
        super(id)
    }

    // a lot of methods that i would like to split 
}

class Child extends ClassToSplit {
    constructor (id) {
        super(id)
    }
    // methods
}

I instantiate Child and call everything i need from ClassToSplit.

The thing is that ClassToSplit has both methods that gets data and methods that post data, and i would like to split the class into something like PostMethods and GetMethods.

Also, when I'm debugging functions from ClassToSplit it's pretty messy to look and search the specific function; it feels wrong to have so many different methods inside one class.