The CSS attribute selector can apply styles based on the attributes and attribute values ??of the element to achieve precise control of specific elements. Style settings are performed by whether there are attributes, exact matches or partial matches attribute values, and combining multiple attribute conditions. For example: 1. When the attribute exists, select: a[download] matches all links with download attributes; 2. Exactly match attribute values: input[type="text"] only matches input boxes with type text; 3. Partial match attribute values: a[href*="example.com"] matches links containing keywords, img[src$=".jpg"] matches pictures ending with .jpg; 4. Multi-condition combination: inputtype="text" matches elements that meet two conditions at the same time. This method is flexible and practical, but excessive nesting should be avoided to affect performance and maintenance.

Sometimes you want to apply specific styles based on the properties of HTML elements, such as making all links with download attributes look different, or adding special borders to certain input boxes. At this time, you can use the CSS attribute selector to implement it.

The attribute selector allows you to select an element by a property or attribute value and style it. It's not difficult to use, but there are several details to pay attention to, especially when you want to match exactly or partially.

Set styles based on whether there is a certain property

The easiest way to use it is to select as long as the element has a certain attribute, no matter its value. For example:

 a[download] {
  color: purple;
}

The meaning of this code is: as long as there is a download attribute in the <a> tag, it will turn it into purple. Regardless of whether download has a value or not, such as <a href="#" download>下載</a> or <a href="#" download="file.txt">下載</a> will be selected.

This writing method is suitable for you to uniformly handle elements that have specific behaviors, such as all downloadable links, all required input boxes ( input[required] ), etc.

Exactly match attribute values

If you want to control more carefully and apply styles only to situations where the attribute values ??are exactly matched, you can use = to make exact matches:

 input[type="text"] {
  border: 1px solid #999;
}

In this way, only the input box with type="text" will apply this border. And those like type="email" or type="number" will not be selected.

This situation is often used for style controls in form controls, where you can set the appearance for different input types separately without affecting other types of input boxes.

Partial matching attribute values

Sometimes you need to do style control based on part of the attribute value, such as a link containing a certain keyword, or a specific string in the class name. At this time, you can use several special symbols:

• *= Includes a certain value (fuzzy match)
• ^= Open with a value
• $= End with a certain value

For example:

 a[href*="example.com"] {
  color: green;
}

The above code will turn all link text containing example.com into green in all link addresses. Whether it is http://example.com or https://www.example.com/path , it applies.

For example, you want to add a border to all pictures ending with .jpg :

 img[src$=".jpg"] {
  border: 2px solid red;
}

These partial matching methods are very practical in actual development, especially if you are not completely sure of the attribute value.

Multi-condition combination

You can also connect multiple attribute selectors together to form a "and" relationship. for example:

 input[type="text"][required] {
  background-color: #f9f9f9;
}

This style will only work on elements that are both text input boxes and required attributes.

This is useful when building complex UI styles and avoids adding additional class names.

In general, the CSS property selector is a very flexible and practical tool. It allows you to complete targeted style control without modifying the HTML structure. Although powerful, it is not recommended to overuse, especially if property values ??are nested too deeply or matched too complex, which may affect performance or maintenance difficulty.

Basically, that's all. Pay attention to the syntax and matching method when using it, and you can easily get the attribute-based style control.

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