API Access

When sending requests, the easiest way is to use json. A helper function may look like the follwing:

const fetchApi = (path = "/", method = "GET", params = {}, accessToken = null, version = API_VERSION) => {
	
	return new Promise((resolve, reject) => {
		let http = new XMLHttpRequest();
	
		http.open(method, API_URL + (version ? "/v" + API_VERSION : '') + "/" + path, true);
		
		if(accessToken !== null){
			http.setRequestHeader("Authorization", "Bearer " + accessToken);
		}
		
		http.onreadystatechange = () => {
			if(http.readyState === 4){
				if(http.status === 200){
					resolve(
						JSON.parse(http.responseText)
					);
				}else{
					reject(Error("Error Code: " + http.status));
				}
			}
		}
		
		http.setRequestHeader("Content-Type", "application/json;charset=UTF-8");
		http.send(JSON.stringify(params));
		
	});
}

Note that this function uses ES6 features such as default parameters and promises, which aren't supported in all browsers yet. You may use a tool like babel in order to make this work all browsers.