function listenForURLChange(cb) {
let body = document.getElementsByTagName("body")[0];
document.addEventListener('onurlchange', (e) => {
cb(e.detail.path);
});
let html = `
let pushState = window.history.pushState;
window.history.pushState = function(state) {
document.dispatchEvent(new CustomEvent('onurlchange', { detail: state }));
return pushState.apply(window.history, arguments);
};`;
let patch = document.createElement("script");
patch.type = 'text/javascript';
patch.innerHTML = html;
body.appendChild(patch);
// Also we'll catch "back" button.
window.onpopstate = (e) => { cb(e.state.path) };
}
