Auto show more for YouTube

This plugin press "Show more" button when display it on your browser by scroll.
当前为 2019-02-03 提交的版本，查看最新版本。
换行
// ==UserScript==
// @name           Auto show more for YouTube
// @name:ja        YouTubeの「もっと見る」ボタンを自動で押す
// @description    This plugin press "Show more" button when display it on your browser by scroll.
// @description:ja YouTube.comの「もっと見る」ボタンが、スクロールによって画面に表示された瞬間、自動で押されます。
// @namespace      https://twitter.com/sititou70
// @license     MIT
// @include        /https*:\/\/www\.youtube\.com\/.*/
// @version        2.1.0
// @grant          none
// ==/UserScript==

//settings
let scroll_event_interval = 100;
const adjust_scroll_px = 0;
const targets = [
    {
        name: "Comment show more button",
        selector: "ytd-expander.ytd-comment-replies-renderer > paper-button#more",
    },
    {
        name: "Watch more related button",
        selector: "yt-next-continuation.ytd-watch-next-secondary-results-renderer > paper-button",
    },
    {
        name: "Video info show more button",
        selector: "ytd-expander.style-scope.ytd-video-secondary-info-renderer > paper-button#more",
    },
];

//global variables
let clicked_buttons = [];

//utils
const user_agent = window.navigator.userAgent.toLowerCase();
const fireClickEvent = (elem) => {
    if( user_agent.match(/(msie|MSIE)/) || user_agent.match(/(T|t)rident/) ) {
        elem.fireEvent("onclick");
    } else {
        const event = document.createEvent("MouseEvents");
        event.initEvent("click", true, true);
        elem.dispatchEvent(event);
    }
};

const getTargetButtons = () =>{
    return targets
        .map(x => document.querySelectorAll(x.selector))
        .reduce((s, x) => [...s, ...x]);
};

//events
let waiting_for_scroll_event_interval = false;
document.addEventListener("scroll", function(){
    if(waiting_for_scroll_event_interval)return;
    waiting_for_scroll_event_interval = true;
    setTimeout(() => waiting_for_scroll_event_interval = false, scroll_event_interval);

    getTargetButtons().forEach(x => {
        if(clicked_buttons.includes(x))return;

        if(x.getBoundingClientRect().y - window.innerHeight + adjust_scroll_px < 0){
            clicked_buttons.push(x);
            fireClickEvent(x);

            //highlight clicked button for debugging
            //x.style.border = "1px solid #f00";
        }
    });
});

document.addEventListener("click", function(e){
    let target = e.target;
    while(target !== document.body){
        if(target.tagName === "A"){
            clicked_buttons = [];
            return;
        }
        target = target.parentElement;
    }
});