Express JS - convert route list in tree

converter.js

let route_list = {};

function print (path, layer) {
	if (layer.route) {
	  layer.route.stack.forEach(print.bind(null, path.concat(split(layer.route.path))))
	} else if (layer.name === 'router' && layer.handle.stack) {
	  layer.handle.stack.forEach(print.bind(null, path.concat(split(layer.regexp))))
	} else if (layer.method) {
		
		const pathRoute = `${layer.method.toUpperCase()} - ${path.concat(split(layer.regexp)).filter(Boolean).join('/')}`;
		const base = pathRoute.split('/')[1];
		
		if (route_list[base]){
			if (!route_list[base].includes(pathRoute))
				route_list[base].push(pathRoute);
		}else{
			route_list[base]=[pathRoute];
		}				  
	}
  }
  
  function split (thing) {
	if (typeof thing === 'string') {
	  return thing.split('/')
	} else if (thing.fast_slash) {
	  return ''
	} else {
	  var match = thing.toString()
		.replace('\\/?', '')
		.replace('(?=\\/|$)', '$')
		.match(/^\/\^((?:\\[.*+?^${}()|[\]\\\/]|[^.*+?^${}()|[\]\\\/])*)\$\//)
	  return match
		? match[1].replace(/\\(.)/g, '$1').split('/')
		: '<complex:' + thing.toString() + '>'
	}
  }
  
app._router.stack.forEach(print.bind(null, []))

console.log(JSON.stringify({
	api:route_list
}))