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HTML

About HTML Preprocessors

HTML preprocessors can make writing HTML more powerful or convenient. For instance, Markdown is designed to be easier to write and read for text documents and you could write a loop in Pug.

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Adding Classes

In CodePen, whatever you write in the HTML editor is what goes within the <body> tags in a basic HTML5 template. So you don't have access to higher-up elements like the <html> tag. If you want to add classes there that can affect the whole document, this is the place to do it.

About the <head>

In CodePen, whatever you write in the HTML editor is what goes within the <body> tags in a basic HTML5 template. If you need things in the <head> of the document, put that code here.

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Insecure Resource

The resource you are linking to is using the 'http' protocol, which may not work when the browser is using https.

CSS

About CSS Preprocessors

CSS preprocessors help make authoring CSS easier. All of them offer things like variables and mixins to provide convenient abstractions.

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CSS Base

About CSS Base

It's a common practice to apply CSS to a page that styles elements such that they are consistent across all browsers. We offer two of the most popular choices: normalize.css and a reset. Or, choose Neither and nothing will be applied.

Vendor Prefixing

About Vendor Prefixing

To get the best cross-browser support, it is a common practice to apply vendor prefixes to CSS properties and values that require them to work. For instance -webkit- or -moz-.

We offer two popular choices: Autoprefixer (which processes your CSS server-side) and -prefix-free (which applies prefixes via a script, client-side).

Add External Stylesheets/Pens

Any URL's added here will be added as <link>s in order, and before the CSS in the editor. If you link to another Pen, it will include the CSS from that Pen. If the preprocessor matches, it will attempt to combine them before processing.

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About External Resources

You can apply CSS to your Pen from any stylesheet on the web. Just put a URL to it here and we'll apply it, in the order you have them, before the CSS in the Pen itself.

If the stylesheet you link to has the file extension of a preprocessor, we'll attempt to process it before applying.

You can also link to another Pen here, and we'll pull the CSS from that Pen and include it. If it's using a matching preprocessor, we'll combine the code before preprocessing, so you can use the linked Pen as a true dependency.

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JavaScript

About JavaScript Preprocessors

JavaScript preprocessors can help make authoring JavaScript easier and more convenient. For instance, CoffeeScript can help prevent easy-to-make mistakes and offer a cleaner syntax and Babel can bring ECMAScript 6 features to browsers that only support ECMAScript 5.

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Babel is required to process package imports. If you need a different preprocessor remove all packages first.

Add External Scripts/Pens

Any URL's added here will be added as <script>s in order, and run before the JavaScript in the editor. You can use the URL of any other Pen and it will include the JavaScript from that Pen.

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About External Resources

You can apply a script from anywhere on the web to your Pen. Just put a URL to it here and we'll add it, in the order you have them, before the JavaScript in the Pen itself.

If the script you link to has the file extension of a preprocessor, we'll attempt to process it before applying.

You can also link to another Pen here, and we'll pull the JavaScript from that Pen and include it. If it's using a matching preprocessor, we'll combine the code before preprocessing, so you can use the linked Pen as a true dependency.

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Behavior

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Format on Save

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HTML 

              
                <input name="print" type="button" value="Print 列印此頁"
onClick="varitext()">
<br/><br/>
<div>
  <h1>列印測試</h1>
  <p>C語言幾乎是當代所有語言的基礎。無論是Ruby, Python(cPython), PHP 或是 Node.js所依賴的V8引擎，裡面都是大量的C語言與C++語法所構成。更不用說常見的作業系統Linux核心和他的變化 - Android系統，甚至是蘋果的iOS與MacOS系統，都含有大量的C語言及其家族程式。</p>
  <p>即使現在較多人提倡的是快速開發，消耗硬體資源換取工程師寶貴的時間。但還是會有很多進階的情況，是必須進入到核心的部分去調校程式。</p>
  <p>在系統資源較缺乏的裝置上 - 例如物聯網相關家電產品，C語言(及其家族程式)幾乎是唯一的工業 / 商業選項。</p>
  <p>畢竟網站主程式多半是只給一台電腦伺服器使用，而產品型商品程式則相反，量產幾乎都是萬台起跳。單一裝置即使只節省一點零件成本，集合起來的利潤也會相當的高。</p>
  <p>所以就工業/商業上，即使新興語言在撰寫與理解上佔有優勢，也很難在短時間取代C語言這"物理"上的優勢。</p>
</div>
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CSS
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JS 

              
                function varitext(){
  var text = document
  print(text)
}
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Console