要向HTML 元素添加屬性，需將其寫在該元素的起始標(biāo)籤內(nèi)。 1. 屬性通常以name/value 對的形式出現(xiàn)，如name="value"；2. 常見屬性包括class、id、style 和href 等；3. 可為一個(gè)元素添加多個(gè)屬性，順序無強(qiáng)制要求但應(yīng)保持可讀性；4. 屬性用於增強(qiáng)功能、樣式、行為及可訪問性等；5. 使用時(shí)應(yīng)注意引號、拼寫規(guī)範(fàn)，並優(yōu)先使用data-* 自定義屬性。

You add attributes to HTML elements by including them inside the opening tag of the element. Attributes provide extra information about an element, like how it should behave or what styling it should have.

Understanding HTML Attributes

HTML attributes are always placed in the opening tag and usually come in name/value pairs like name="value" . For example, the src attribute in an <img src="/static/imghw/default1.png" data-src="photo.jpg" class="lazy" alt="如何將屬性添加到HTML元素？" > tag tells the browser where to find the image:

 <img  src="/static/imghw/default1.png"  data-src="photo.jpg"  class="lazy" alt="如何將屬性添加到HTML元素？" >

Here, src is the attribute name and "photo.jpg" is the value. Most attributes are case-insensitive, but values are often case-sensitive depending on the context.

Some common attributes you'll see include:

• class – used for styling with CSS
• id – a unique identifier for an element
• style – inline CSS for that specific element
• href – used in links ( <a> ) to point to another page or resource

Adding Multiple Attributes

You can add more than one attribute to a single HTML element by placing them one after another inside the opening tag:

 <a href="https://example.com" target="_blank" class="link-style">Visit Example</a>

In this example:

• href defines the link destination.
• target="_blank" makes the link open in a new tab.
• class="link-style" allows you to style this link using CSS.

There's no strict order for attributes, but people usually list them in a logical or readable way — often starting with required ones like href or src .

When and Why You Should Use Attributes

Attributes help make your HTML more functional and interactive. Here are some typical use cases:

• Accessibility : Use alt on images so screen readers can describe them.
• Forms : Add required , placeholder , or type to input fields.
• Styling : Use class or style to apply visual changes.
• Behavior : Some JavaScript relies on data attributes like data-id or data-role .

For example, form validation can be as simple as adding required :

 <input type="text" name="username" required>

This tells the browser not to let the user submit the form unless that field is filled in.

A Few Things to Watch Out For

While adding attributes seems straightforward, here are a few gotchas:

• Always quote attribute values unless they're simple and contain no spaces or special characters (but quoting is still safer).
• Don't misspell attribute names — browsers might ignore them.
• Avoid using custom attributes unless you're using data-* attributes, which are meant for storing custom data.

For example, this is risky:

 <div my-attribute="test"></div>

Instead, do this:

 <div data-myattribute="test"></div>

It's small stuff, but doing it right helps avoid bugs later.

基本上就這些。 Adding attributes is a basic but essential part of working with HTML, and once you get the pattern down, it becomes second nature.

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