Logic outside of React

some.js

// -- bit excessive for this case, but the example isn't realistic in the first place
export const probability = () => Math.random(); 

// -- some other file
export const diceRoll = () => Math.ceil(probability() * 6);

// -- some other file
export const coinFlip = () => probability() > 0.5 ? 'heads': 'tails';

// -- shared state can be stored however you like (this is just one example)
export let wisdom = diceRoll();
const callbacks = [];
export const listen = callback => callbacks.push(callback);
export const rollForWisdom = () => {
    wisdom = diceRoll();
    callbacks.forEach(cb => cb(wisdom));
};

// -- still consumable in React, or anywhere. Can share state with non-React code too.
class Probability extends Component {
    constructor(props) {
        super(props);
        this.state = wisdom;
        listen(wisdom => this.setState(wisdom));
    }
    render() {
        return this.props.children({ rerun: rollForWisdom, result: this.state });
    }
}