Customizing node props

auto_classnames.jsx

import { options } from 'preact';
import cx from 'classnames';

let old = options.vnode;
options.vnode = vnode => {
  let isElement = typeof vnode.nodeName==='string',
    props = vnode.attributes || {},
    key = props.class ? 'class' : 'className';
  if (isElement && props[key] && typeof props[key]==='object') {
    props[key] = cx(props[key]);
  }
  if (old) old(vnode);
};

general_props.jsx

import { options } from 'preact';

let old = options.vnode;
options.vnode = vnode => {
  // vnode.attributes is your props
  // this gets run on every element.
  if (old) old(vnode);
};