class AsyncManager { protected readonly url: string = "/admin/async"; constructor(url?: string) { if (url !== undefined) this.url = url; } public getTaskList(onSuccess: Function, onError?: Function): void { let xhr = new XMLHttpRequest(); xhr.open("GET", this.url + ".json", true); xhr.send(); // @todo Continue } } let async: AsyncManager = new AsyncManager(); const url = "/admin/async"; let xhr = new XMLHttpRequest(); xhr.open("GET", url + ".json", true); xhr.send(); xhr.onload = function () { if (xhr.status === 200) { } }