Tampermonkey script to define my personal key mapping using in chrome browser <3

MyKeyMap.js

// ==UserScript==
// @name         MyKepMap
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  try to take over the world!
// @author       weaming
// @match        *://*/*
// @grant        none
// ==/UserScript==

(function() {
  "use strict";
  window.print = console.log.bind(console);
  let leader = ",";
  let maxLen = 3;
  let KS = {
    empty: () => {
      window.keyStack = [];
    },
    push: v => {
      if (window.keyStack === undefined) {
        window.keyStack = [];
      }
      window.keyStack.push(v);
    },
    len: () => {
      if (window.keyStack) {
        return window.keyStack.length;
      }
      return 0;
    },
    value: () => {
      if (window.keyStack) {
        return window.keyStack;
      }
      return [];
    }
  };

  document.addEventListener("keydown", e => {
    print(e);
    if (e.key === "Escape") {
      KS.empty();
      return;
    }
    if (KS.len() >= maxLen) {
      KS.empty();
    }

    if (KS.len() === 0) {
      if (e.key === leader) {
        KS.empty();
        KS.push(e.key);
        return;
      }
    } else {
      if (KS.value()[0] === leader && e.key.length === 1) {
        KS.push(e.key);
      }
    }

    let ks = KS.value()
      .slice(1)
      .join("");
    if (ks.length > 0) {
      print(ks);
      e.preventDefault();
    }

    if (ks === ".") {
      KS.empty();
      // goto root
      location.href = location.origin;
      return;
    }
    if (ks === ",") {
      KS.empty();
      // goto upper
      location.search = "";
      let newPath = location.pathname
        .split("/")
        .filter(x => x.length > 0)
        .slice(0, -1)
        .join("/");
      location.pathname = newPath;
      return;
    }
    if (ks === "a") {
      KS.empty();
      // goto raw file of github source code
      location.href = location.href
        .replace("github.com", "raw.githubusercontent.com")
        .replace("/blob/", "/");
      return;
    }
  });
})();