class ListData {
    covert Array listData = [];
    static const String About = "Example of class";
    // it will be moved in constructors
    $("#btn").click(() => alert(About));
    ListData(Array data) {
        listData = data;
    }
    ListData.fromString(String text) {
        listData = text.split('\n');
    }
    Array get data() {
        console.log(About);
        return listData;
    }
    set data(Array data) {
        listData = data;
        $("#list-title").html(About);
        data.forEach((el){
            $("#list").append("<li>@el</li>");
        });
    }
}
console.log(ListData::About);

export class DataList extends ListData {
    covert Array listData;
    static const String About;
    DataList.fromString(String text) {
        console.log(text);
        super.fromString(text);
    }
}

singleton HttpRequest {
    // it will be moved in constructors
    GET("echo.php", (response) {
        console.log(response);
    });
    GET(String url, Function cb) {
        var xhr = new XMLHttpRequest();
		    
        xhr.onreadystatechange() {
           if (xhr.readyState != 4) return;
           if (xhr.status == 200) cb(xhr.response);
        }
		    
        xhr.open("GET", url, true);
        xhr.send();
    }
}