How do I detect dark mode using JavaScript?

Windows and macOS now have dark mode.

For CSS I can use:

@media (prefers-dark-interface) { 
  color: white; background: black 
}

But I am using the Stripe Elements API, which puts colors in JavaScript

For example:

const stripeElementStyles = {
  base: {
    color: COLORS.darkGrey,
    fontFamily: `-apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", "Noto Color Emoji"`,
    fontSize: '18px',
    fontSmoothing: 'antialiased',
    '::placeholder': {
      color: COLORS.midgrey
    },
    ':-webkit-autofill': {
      color: COLORS.icyWhite
    }
  }
}

How can I detect the OS's preferred color scheme in JavaScript?

if (window.matchMedia && window.matchMedia('(prefers-color-scheme: dark)').matches) {
    // dark mode
}

To watch for changes:

window.matchMedia('(prefers-color-scheme: dark)').addEventListener('change', event => {
    const newColorScheme = event.matches ? "dark" : "light";
});