【TypeScript】JQueryを使わずページをヌルっとスクロールさせる

JQueryを使わず、且つ、TypeScriptを使ってページをヌルっとスクロールさせたい！

手順書

実際のコードを下記に示す。

class Scroll {
    constructor() {
        const duration: number = 500;

        window.addEventListener("DOMContentLoaded", () => {
            const scrollTriggers: HTMLElement[] = [].slice.call(document.querySelectorAll('a[href^="#"]'));
            scrollTriggers.forEach((scrollTrigger) => {
                scrollTrigger.addEventListener("click", (e) => {
                    const href: string = scrollTrigger.getAttribute("href") as string;
                    if (href) {
                        const currentPosition: number = document.documentElement.scrollTop || document.body.scrollTop;
                        const targetElement: HTMLElement = document.getElementById(href.replace("#", "")) as HTMLElement;
                        if (targetElement) {
                            e.preventDefault();
                            e.stopPropagation();
                            const targetPosition: number = window.pageYOffset + targetElement.getBoundingClientRect().top;
                            const startTime: number = performance.now();
                            const loop = (nowTime: number) => {
                                const time: number = nowTime - startTime;
                                const normalizedTime: number = time / duration;
                                if (normalizedTime < 1) {
                                    window.scrollTo(0, currentPosition + ((targetPosition - currentPosition) * this.easeInOut(normalizedTime)));
                                    requestAnimationFrame(loop);
                                } else {
                                    window.scrollTo(0, targetPosition);
                                }
                            };

                            requestAnimationFrame(loop);
                        }
                    }
                });
            });
        });
    }

    easeInOut(t: number) {
        return t < .5 ? 4 * t * t * t : (t - 1) * (2 * t - 2) * (2 * t - 2) + 1;
    }
}

const scroll = new Scroll();

感想文（まとめ）

何でもかんでもTypeScriptにしたい。