Кнопка для скрытия панели навигации

// ==UserScript==
// @name Hide frame
// @namespace 0chan
// @include https://0chan.hk/*
// @version 1
// @grant none
// ==/UserScript==

var label_style = document.createElement("style");
label_style.innerHTML = ".label {background-color:rgb(44, 51, 61);cursor: pointer; width: 30px; height: 50px; border-radius: 0px 3px 3px 0px; padding: 3px 1px 3px 1px; display: table; font-size: 20px;}"
document.head.appendChild(label_style);
var label = document.createElement("div");
var arrows = document.createElement("span");

arrows.innerHTML = "<<";
arrows.style.display = "table-cell";
arrows.style.verticalAlign = "middle";
label.appendChild(arrows);
label.className = "label";
label.style.position = "fixed";
label.style.left = "250px";
label.style.top = "50%";
label.style.transitionDuration = "0.5s";

var sidebar;
var content;
function hideSidebar()
{
sidebar = document.getElementById("sidebar");
content = document.getElementById("content");
if(sidebar === null || content === null)
return;
sidebar.style.transitionDuration = "0.5s";
content.style.transitionDuration = "0.5s";
sidebar.style.left = "-250px";
content.style.marginLeft = "0px";
label.style.left = "0px";
label.onclick = showSidebar;
arrows.innerHTML = ">>";
}
function showSidebar()
{
sidebar = document.getElementById("sidebar");
content = document.getElementById("content");
if(sidebar === null || content === null)
return;
sidebar.style.transitionDuration = "0.5s";
content.style.transitionDuration = "0.5s";
sidebar.style.left = "0px";
content.style.marginLeft = "250px";
label.style.left = "250px";
label.onclick = hideSidebar;
arrows.innerHTML = "<<";
}
document.body.appendChild(label);
label.onclick = hideSidebar; //HTML-cookie saving?

Скрипт кнопки скрытия боковой панели