mainonly

Intro Page

A JavaScript bookmarklet designed to isolate and highlight a specific element on a webpage, effectively hiding all other elements.

(Created with GPT-4-turbo-1106 and refined through manual adjustments.)

How to Use

1. Copy the following code:

   javascript:(function(){document.getElementById("mainonly")&&document.dispatchEvent(new KeyboardEvent("keydown",{key:"Escape"}));var e=document.body,n=null;e.id?(n="class",e.classList.add("mainonly")):(n="id",e.id="mainonly");let t=document.head.appendChild(document.createElement("style"));t.textContent="#mainonly { outline: 2px solid red; }  .mainonly { outline: 2px solid red; }";let i=document.body.appendChild(document.createElement("div"));i.className="mainonly-guide",i.innerHTML=`<p>正在选择元素。按 <kbd>Esc</kbd> 键取消选择。向下滚动，或按下 <kbd>=</kbd>/<kbd>.</kbd> 键缩小选区。向上滚动，或按下 <kbd>-</kbd>/<kbd>,</kbd> 键扩大选区。</p><p>Selecting element. Press <kbd>Esc</kbd> to cancel selection. Scroll down, or press <kbd>=</kbd>/<kbd>.</kbd> to shrink the selection. Scroll up, or press <kbd>-</kbd>/<kbd>,</kbd>, to expand the selection.</p>`;let o=document.head.appendChild(document.createElement("style"));function l(t){t instanceof HTMLElement&&("id"===n?e.removeAttribute("id"):e.classList.remove("mainonly"),(e=t).id?(n="class",e.classList.add("mainonly")):(n="id",e.id="mainonly"))}function d(e){l(e.target)}function a(i){i.preventDefault(),function n(){for(var t=e;t.parentElement;)(t=t.parentElement).classList.add("mainonly_parents")}(),"id"===n?t.textContent="* { visibility: hidden; } #mainonly, #mainonly *, .mainonly_parents { visibility: visible; }":t.textContent="* { visibility: hidden; } .mainonly, .mainonly *, .mainonly_parents { visibility: visible; }",m(),r()}function r(){i.remove(),o.remove()}function s(i){if(i.preventDefault(),"Escape"===i.key)t.remove(),document.removeEventListener("keydown",s),m(),r(),"id"===n?e.removeAttribute("id"):e.classList.remove("mainonly"),function e(){for(var n=document.querySelectorAll(".mainonly_parents"),t=0;t<n.length;t++)n[t].classList.remove("mainonly_parents")}();else if(","===i.key||"-"===i.key)l(e.parentElement);else if("."===i.key||"="===i.key){var o=e.querySelector(":hover");o&&l(o)}}function c(n){if(n.preventDefault(),n.deltaY<0)l(e.parentElement);else{var t=e.querySelector(":hover");t&&l(t)}}function m(){document.removeEventListener("mouseover",d),document.removeEventListener("click",a),document.removeEventListener("wheel",c)}o.textContent=` .mainonly-guide { position: fixed; top: 0; left: 50%; /* center the box horizontally */ transform: translate(-50%, 0); /* center the box horizontally */ padding: 0.5rem; font-size: 1rem; font-family: sans-serif; text-align: center; color: white; background-color: rgba(0, 0, 0, 0.5); border-radius: 0.5em; z-index: 999999999;     kbd { display: inline-block; padding: 0.1em 0.3em; font-size: 0.8em; line-height: 1; color: #24292e; vertical-align: middle; background-color: #fafbfc; border: 1px solid #d1d5da; border-radius: 3px; box-shadow: inset 0 -1px 0 #d1d5da;     } }`,document.addEventListener("mouseover",d),document.addEventListener("click",a),document.addEventListener("wheel",c,{passive:!1}),document.addEventListener("keydown",s)}())

2. Right-click on your browser's bookmark bar and select "Add Bookmark".

3. In the pop-up window, name your bookmark (for example, "mainonly") and paste the copied code into the URL or location field.

4. Save the bookmark.

5. On a webpage, activate the bookmarklet, then click on the element you want to focus on. This element will be encircled with a red outline. Use the scroll wheel or keyboard shortcut (- , for expand, = . for shrink) to adjust the selection size.

6. Once you've made a selection, click the left mouse button. All other elements will be hidden, leaving only the selected element visible.

7. Press the ESC key to reveal the hidden elements and revert the page to its original state.

Tools

• minifier
• Bookmarklet Maker

How it Works?

• The onhover event selects the element that is being hovered over.
• When scrolling, the parent or child node of the currently selected element is obtained.
• When clicked, the selected element is assigned an id or class attribute.
• CSS visibility: hidden; is used to hide the other elements.

(Or just read the code and see for yourself.)

Is it Safe?

Yes, it is safe. The code is executed locally on the user's device and does not make any network requests. It only interacts with the webpage that is currently open in the browser.

What are the limitations?

• In some web pages, other parts of the text content outside the selected element may still be visible. (This issue only occurs when the selected element already has an id attribute; it is a limitation of the browser itself and currently has no solution.)

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介绍页面

一个 JavaScript 书签工具，专门用于隐藏网页上的非目标元素，仅显示您想要聚焦的元素。

（基于 GPT-4-turbo-1106 创制，并经过手动优化调整。）

使用方法

1. 复制以下代码：

   javascript:(function(){document.getElementById("mainonly")&&document.dispatchEvent(new KeyboardEvent("keydown",{key:"Escape"}));var e=document.body,n=null;e.id?(n="class",e.classList.add("mainonly")):(n="id",e.id="mainonly");let t=document.head.appendChild(document.createElement("style"));t.textContent="#mainonly { outline: 2px solid red; }  .mainonly { outline: 2px solid red; }";let i=document.body.appendChild(document.createElement("div"));i.className="mainonly-guide",i.innerHTML=`<p>正在选择元素。按 <kbd>Esc</kbd> 键取消选择。向下滚动，或按下 <kbd>=</kbd>/<kbd>.</kbd> 键缩小选区。向上滚动，或按下 <kbd>-</kbd>/<kbd>,</kbd> 键扩大选区。</p><p>Selecting element. Press <kbd>Esc</kbd> to cancel selection. Scroll down, or press <kbd>=</kbd>/<kbd>.</kbd> to shrink the selection. Scroll up, or press <kbd>-</kbd>/<kbd>,</kbd>, to expand the selection.</p>`;let o=document.head.appendChild(document.createElement("style"));function l(t){t instanceof HTMLElement&&("id"===n?e.removeAttribute("id"):e.classList.remove("mainonly"),(e=t).id?(n="class",e.classList.add("mainonly")):(n="id",e.id="mainonly"))}function d(e){l(e.target)}function a(i){i.preventDefault(),function n(){for(var t=e;t.parentElement;)(t=t.parentElement).classList.add("mainonly_parents")}(),"id"===n?t.textContent="* { visibility: hidden; } #mainonly, #mainonly *, .mainonly_parents { visibility: visible; }":t.textContent="* { visibility: hidden; } .mainonly, .mainonly *, .mainonly_parents { visibility: visible; }",m(),r()}function r(){i.remove(),o.remove()}function s(i){if(i.preventDefault(),"Escape"===i.key)t.remove(),document.removeEventListener("keydown",s),m(),r(),"id"===n?e.removeAttribute("id"):e.classList.remove("mainonly"),function e(){for(var n=document.querySelectorAll(".mainonly_parents"),t=0;t<n.length;t++)n[t].classList.remove("mainonly_parents")}();else if(","===i.key||"-"===i.key)l(e.parentElement);else if("."===i.key||"="===i.key){var o=e.querySelector(":hover");o&&l(o)}}function c(n){if(n.preventDefault(),n.deltaY<0)l(e.parentElement);else{var t=e.querySelector(":hover");t&&l(t)}}function m(){document.removeEventListener("mouseover",d),document.removeEventListener("click",a),document.removeEventListener("wheel",c)}o.textContent=` .mainonly-guide { position: fixed; top: 0; left: 50%; /* center the box horizontally */ transform: translate(-50%, 0); /* center the box horizontally */ padding: 0.5rem; font-size: 1rem; font-family: sans-serif; text-align: center; color: white; background-color: rgba(0, 0, 0, 0.5); border-radius: 0.5em; z-index: 999999999;     kbd { display: inline-block; padding: 0.1em 0.3em; font-size: 0.8em; line-height: 1; color: #24292e; vertical-align: middle; background-color: #fafbfc; border: 1px solid #d1d5da; border-radius: 3px; box-shadow: inset 0 -1px 0 #d1d5da;     } }`,document.addEventListener("mouseover",d),document.addEventListener("click",a),document.addEventListener("wheel",c,{passive:!1}),document.addEventListener("keydown",s)}())

2. 右键点击您的浏览器书签栏，选择“添加书签”。

3. 在弹出的窗口中，为书签命名（例如：“mainonly”），并将复制的代码粘贴到 URL 或位置栏中。

4. 保存书签。

5. 在网页上，激活书签后，点击您想要关注的元素。该元素将被红色轮廓圈出。使用滚轮或键盘快捷键（- , 扩大, = . 缩小）调整选择范围。

6. 选定元素后，点击鼠标左键，其他所有元素将被隐藏，只显示所选元素。

7. 按 ESC 键可显示隐藏的元素，并恢复网页至原始状态。

工具

• minifier （代码压缩工具）
• Bookmarklet Maker （小书签制作工具）

工作原理

• onhover 事件选择被悬停的元素。
• 滚动时，获取当前选定元素的父节点或子节点。
• 点击时，为选定的元素分配 id 或 class 属性。
• 使用 CSS 的 visibility: hidden; 来隐藏其他元素。

（或者直接阅读代码。）

是否安全？

是的，它是安全的。该代码在用户设备上本地执行，不会进行任何网络请求。它只与当前在浏览器中打开的网页进行交互。

有什么限制？

• 部分网页中，选中元素之外的其他部分文本内容依然可见。（此问题仅在被选中的元素已有 id 属性时出现；这是浏览器本身的限制，暂时没有解决方案。）