tampermonkey ptt hjkl keyboard

hjkl.js

// ==UserScript==
// @name         ptt hjkl keyboard
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  right hand keyboard to navigate term.ptt.cc
// @author       Ingram Chen
// @match        https://term.ptt.cc/
// @icon         https://www.google.com/s2/favicons?sz=64&domain=ptt.cc
// @grant        none
// ==/UserScript==

/**
  Press x to disable navigation mode
  Press Esc to enable navigation mode
  Use `:` as help replacement
  see handleKeys() for more keymapping, customize for your own needs.
 */
(function() {
    'use strict';

    function sendKey(key, keyCode) {
        let type = "keydown";
        if (key.length === 1) {
            type = "keypress";
        }
        window.dispatchEvent(new KeyboardEvent(type, {
            keyCode: keyCode,
            key: key
        }));
        //console.debug(event.target);
    }

    function stopKey(event, key) {
      if (event.key === key) {
         event.stopPropagation();
         event.preventDefault();
         console.debug(`stopped ${key}`);
         return true;
      }
      return false;
    }

    function switchKey(event, fromKey, toKey, toKeyCode) {
        if (stopKey(event, fromKey)) {
            sendKey(toKey, toKeyCode);
        }
    }

    let triggering = false;
    function handleKeys(event) {
        try {
          if (triggering) {
            return;
          }
          triggering = true;
          switchKey(event, 'h', 'ArrowLeft', 37);
          switchKey(event, ':', 'h', 72); // `:` replace as help
          switchKey(event, '8', 'Home', 36);
          switchKey(event, 'i', 'End', 35);
          switchKey(event, '9', 'PageUp', 33);
          switchKey(event, 'o', 'PageDown', 34);
        } finally {
          triggering = false;
        }
    }

    let enabled = true;
    function handleMode(event) {
        if (event.key === 'x') {
          //推文開始時關閉
          enabled = false;
          return;
        }

        if (event.key === `Escape`) {
          //Esc 重新開始
          enabled = true;
          return;
        }

        if (!enabled) {
          return;
        }

        handleKeys(event);
    }

    document.addEventListener("keydown", (event)=> {
       handleMode(event);
    }, true);
})();