win/mac/linux theme change listener for react

someComponent.jsx

import React from 'react';
import { themeChange } from '../../../style/theme';
...
themeChange.subscribe(console.log); // logs dark/light

theme.js

/* theme file for react-jss */
const theme = {};
const themeChange = {
    listeners: [],
    subscribe: cb => themeChange.listeners.push(cb)
}

const isDark = window.matchMedia('(prefers-color-scheme: dark)');
isDark.addListener(evt=>{
    if(evt.matches) theme.colorPrimary = 'yellow';
    else theme.colorPrimary = 'red';
    themeChange.listeners.forEach(handler => handler(evt.matches?'dark':'light'))
});

if(isDark.matches) theme.colorPrimary = 'yellow';
else theme.colorPrimary = 'red';

export { theme as default, themeChange }