CSS - Attr Selectors

Ethan D. - May 31, 2024

Syntax and Usage

Attribute selectors in CSS let you target elements based on their attributes. The basic syntax of an attribute selector consists of square brackets [] containing the attribute name. You can refine the selection by specifying the attribute value or using special operators.

To target an element with a specific attribute, use this syntax:

Example: Basic Attribute Selector

[attribute] {
  /* CSS styles */
}

To select all <a> elements with a target attribute, use:

Example: Selecting `<a>` Elements with a target Attribute

a[target] {
  /* CSS styles */
}

You can also target elements based on the value of an attribute. To do this, append an equals sign = and the attribute value within quotes after the attribute name:

Example: Attribute Selector with Specific Value

[attribute="value"] {
  /* CSS styles */
}

To select all <img> elements with an alt attribute value of "logo", use:

Example: Selecting Elements with Specific alt Attribute

img[alt="logo"] {
  /* CSS styles */
}

Some common attribute selectors include:

[class]: Selects elements with a class.
[id]: Selects elements with an id.
[type]: Selects input types.
[disabled]: Selects disabled elements.
[required]: Selects required elements.

Examples of using these selectors:

Example: Specific Attribute Selectors

/* Select all input elements with a type of "text" */
input[type="text"] {
  /* CSS styles */
}

/* Select all elements with a "data-toggle" attribute */
[data-toggle] {
  /* CSS styles */
}

/* Select all elements with a "title" containing "example" */
[title*="example"] {
  /* CSS styles */
}

Attribute selectors give you a way to select and style specific parts of your web page based on their attributes.

Types of Attribute Selectors

CSS attribute selectors come in several types, each with its own syntax and purpose. Here are the different types of attribute selectors and how to use them.

Presence Selector

The presence selector targets elements that have a specified attribute, regardless of its value. The syntax for the presence selector is:

Example: Syntax for presence selector

[attribute] {
  /* CSS styles */
}

To select all <a> elements that have a title attribute:

Example: Select all `<a>` elements with a title attribute

a[title] {
  /* CSS styles */
}

This selector will match any <a> element with a title attribute, no matter what the value of the attribute is.

Equality Selector

The equality selector targets elements with an attribute value equal to a specified value. The syntax for the equality selector is:

Example: Syntax for equality selector

[attribute="value"] {
  /* CSS styles */
}

To select all <input> elements with a type attribute value of "submit":

Example: Select all `<input>` elements with type='submit'

input[type="submit"] {
  /* CSS styles */
}

By default, the equality selector is case-sensitive. To perform a case-insensitive match, add an i before the closing bracket:

Example: Case-insensitive equality selector

[attribute="value" i] {
  /* CSS styles */
}

Substring Selectors

Substring selectors target elements with an attribute value containing a specified substring. There are three types of substring selectors:

Begins with selector ([attribute^="value"]): Selects elements with an attribute value starting with the specified value.
Ends with selector ([attribute$="value"]): Selects elements with an attribute value ending with the specified value.
Contains selector ([attribute*="value"]): Selects elements with an attribute value containing the specified value anywhere within the string.

Examples of each substring selector:

Example: Select with attribute beginning with value

[data-category^="top"] {
  /* CSS styles */
}

Example: Select with attribute ending with value

[href$=".pdf"] {
  /* CSS styles */
}

Example: Select with attribute containing value

[class*="featured"] {
  /* CSS styles */ 
}

Suffix and Prefix Selectors

Suffix and prefix selectors are similar to begins-with and ends-with substring selectors but match entire values rather than just parts.

Prefix: [attribute|='value']: Matches attributes equal or starting followed by hyphen (-).
Suffix: Not supported in CSS

Example:

Example: Prefix selector for languages

/* Matches lang='en' or starts 'en-'*/ 
 [lang|='en'] {   
   /* CSS styles */
 }

Combining Attribute Selectors

You can use multiple attribute selectors together to target specific elements based on more than one attribute. This allows for precise and complex selections. You can also combine attribute selectors with other CSS selectors, such as class, id, or element selectors.

To combine attribute selectors, write them one after another within the same selector:

Example: Combining Attribute Selectors

[attribute1][attribute2] {
  /* CSS styles */
}

To select all <input> elements with a type attribute of "text" and a required attribute:

Example: Selecting Specific Input Elements

input[type="text"][required] {
  /* CSS styles */
}

You can also mix attribute selectors with other CSS selectors.

Example: Mixing Attribute Selectors with Class Selectors

a.button[data-type="primary"] {
  /* CSS styles */
}

Here are a few more examples of complex combinations:

Example: Selecting Elements with Multiple Attributes

/* Select <img> elements with a "data-src" attribute and an "alt" attribute containing "avatar" */
img[data-src][alt*="avatar"] {
  /* CSS styles */
}

/* Select <div> elements with a "role" attribute of "alert" and a "data-type" starting with "warning" */
div[role="alert"][data-type^="warning"] {
  /* CSS styles */
}

/* Select <a> elements with an "href" ending with ".pdf" and a "target" of "_blank" */
a[href$=".pdf"][target="_blank"] {
  /* CSS styles */
}

By combining these methods, you can build very specific selections to apply styles to elements based on certain attributes. This gives you flexibility and control over your page styling.

Practical Applications

Attribute selectors have many uses in web development. They allow you to style elements based on their attributes, making it easier to target specific elements without adding extra classes or IDs. Here are some examples of how attribute selectors can be used:

Styling Form Elements

Attribute selectors are commonly used to style form elements based on their attributes.

Example: Styling required form fields

input[required], 
textarea[required] {
  border: 1px solid red;
}

You can also style form elements based on their type:

Example: Styling form elements by type

input[type="text"] {
  background-color: #f0f0f0;
}

input[type="submit"] {
  background-color: #4CAF50;
  color: white;
}

Styling Links

Attribute selectors can be used to style links based on their href attribute.

Example: Adding icon to external links

a[href^="http"]:after {
  content: "↗️";
}

You can also style links that point to a specific file type, like PDFs:

Example: Styling PDF links

a[href$=".pdf"] {
  background-image: url('pdf-icon.png');
  padding-left: 20px;
}

Targeting Custom Data Attributes

HTML5 introduced custom data attributes, which allow you to store extra information on elements. You can use attribute selectors to target these custom attributes and apply styles based on their values.

Example: Styling custom data attributes

<div data-theme="dark">Dark Mode</div>
<div data-theme="light">Light Mode</div>

[data-theme="dark"] {
  background-color: #333;
  color: white;
}

[data-theme="light"] {
  background-color: white;
  color: #333;
}

Internationalization

Attribute selectors can be used for styling elements based on the lang attribute, which specifies the language of the element's content. This is useful for sites that support multiple languages.

Example: Styling based on language

[lang|="en"] {
  font-family: "English Font", sans-serif;
}

[lang|="ja"] {
  font-family: "Japanese Font", serif.
}

Best Practices

When using attribute selectors in your CSS, follow some best practices to keep your code efficient and maintainable. Here are some tips:

Write Efficient Selectors

While attribute selectors are helpful, overusing them can lead to complex and inefficient CSS. Use them sparingly and combine them with classes or other simpler selectors when possible.

Example: Write Efficient Selectors

/* Less efficient */
[data-type="button"][data-size="large"][data-color="primary"] {
  /* styles */
}

/* More efficient */
.btn-lg-primary {
  /* styles */
}

Avoid Overuse

Avoid using attribute selectors for styling large numbers of elements. Applying styles to elements like [class] or [href] can match many elements and slow down your page. Instead, use more specific selectors or classes.

Example: Avoid Overuse

/* Avoid this */
[href] {
  color: blue;
}

/* Instead, use a class or more specific selector */
a {
  color: blue;
}

Consider Specificity

Attribute selectors have higher specificity than class, pseudo-class, or element selectors but lower specificity than IDs. This means that styles applied with attribute selectors can be hard to override.

To manage specificity, try to use attribute selectors in combination with classes rather than on their own. This makes your styles more modular and easier to work with.

Example: Consider Specificity

/* Higher specificity, harder to override */
[type="text"] {
  border: 1px solid black;
}

/* Lower specificity, more modular */
.text-input[type="text"] {
  border: 1px solid black;
}