sleeper.js

export default (function create(options = {}) {
	const client = {
		headers: options.headers || {},
		create
	};
	const events = {};

	client.emit = (type, e) => {
		events[type] &&
			events[type].slice().map(fn => {
				fn(e);
			});
	};

	client.on = (type, fn) => {
		(events[type] || (events[type] = [])).push(fn);
	};

	client.off = (type, fn) => {
		events[type] && events[type].splice(events[type].indexOf(fn) >>> 0, 1);
	};

	client.bind = (url, config) => (...args) => client.request(
		url.replace(/:[a-z]+/g, (s, f) => encodeURIComponent(args.shift())),
		args.pop(),
		config
	);

	client.request = (url, body, config) => {
		let method;
		url = url.replace(/^([A-Z]+) /,(s,m)=>method=m&&'');
		const req = Object.assign({}, config, {
			method,
			url: (options.url || '') + url,
			headers: Object.assign({}, client.headers, config && config.headers)
		});
		if (body) {
			if (method > 'I') {
				req.body = body;
				if (typeof (req.body = body) == 'object') {
					req.body = JSON.stringify(body);
					req.headers['Content-Type'] = 'application/json';
				}
			} else {
				req.url += '?' + new URLSearchParams(body);
			}
		}
	
		client.emit('before', req);
	
		let res;
		return fetch(req.url, req)
			.then(r => (res = r).json())
			.then(data => {
				res.data = data;
				res.request = req;
				client.emit('after', res);
				if (res.ok) return data;
				throw Object.assign(Error(res.statusText), {
					data,
					request: req
				});
			});
	}

	['get','post','put','patch', 'delete'].map(m => client[m] = (a,b,c)=>client.request(m.toUpperCase()+' '+a,b,c));

	return client;
})();