In this tutorial, you will use the id, class, and attribute selectors to scope styles to intentionally written HTML. You will begin by creating an HTML and a CSS file that you will edit throughout the tutorial. You will then add id attributes and use those id values to target styles.
You will also add class attributes to elements and use those class values independently and together to create more specific and reusable styles. Lastly, you will use the attribute selector to create styles that match much more specific scenarios than an id or class selector alone can accomplish. Besides the obvious utility of selecting elements with an exactly matching data attribute, there are a lot more things we can achieve with CSS attribute selectors. In general, the attribute selector can target any attribute that's attached to an HTML element.
By default, the selector is case sensitive and has a lower specificity than id's and classes. After adding the class attributes to the elements in the index.html file, be sure to save the changes. Then, open styles.css in your text editor and create a class selector for the style-1 class. In this section, you will use the class selector to find specific element on a page using values found in the class HTML attribute. You will refactor the id selectors to use a reusable class instead. The class attribute is meant to create a specific targetable value that styles can be applied to.
Unlike the id, the values of class attributes can be reused, which is its advantage over the id selector. When styling a text input, we generally would not want the same styles to apply to a checkbox. Of course, we can also use multiple attribute selectors simultaneously to select specific elements. This can be especially handy when the HTML provides us with enough info to create different styles only through our attributes. Let's say we want to give icons to every file download link on a site and a special icon to PDFs. We can combine the contains and ends with selectors to select all files and then specifically find all PDFs.
The type selector identifies an element based on its type, specifically how that element is declared within HTML. The class selector identifies an element based on its class attribute value, which may be reused on multiple elements as necessary to help share popular styles. Lastly, the ID selector identifies an element based on its ID attribute value, which is unique and should only be used once per page. Is either a type selector or universal selector followed immediately by zero or more attribute selectors, ID selectors, or pseudo-classes, in any order.
The simple selector matches if all of its components match. Writing styles that are specific and reusable is a cornerstone to effective CSS architecture. These selectors are a powerful asset to create styles that bring life and functionality to a website. To begin styling with an attribute selector, open the styles.css file in your text editor. Add an attribute selector for and then curly brackets for the selector block. In the selector block, add the text-decoration property set to underline.
Then add the text-decoration-style property with a value of dotted. These two properties will equalize the styling across browsers. Lastly, to add a custom look for the underline, add the property text-decoration-color and set it to a light gray with the value hsl(0, 0%, 70%) . Note that the new styling you declared for the combined class selectors will take precedence over the style set for each of the individual classes.
This is because the combined class selector is selecting a more specific element than the individual class selectors. For example, the rule you wrote for .color-1 is looking for an HTML element that has color-1 as one of its classes. The .color-1.color-2 rule is looking for an HTML element that has both color-1 and color-2 in the list of its classes. Since the second rule is a subset of the first, it can be said to be more specific, and thus overrides the first. In this section, you will apply multiple class values to the same HTML element to combine the styles from more than one CSS class selector.
The advantage of class over id is its reusability, as shown in the previous section. Class selectors can also be combined to target more specific elements. The class selector is the most common and preferred CSS selector for this versatility and specificity in finding an element and applying styles. In this section, you learned about the id attribute and used this attribute to apply styles to elements. You also learned that the id attribute is required to have a unique value because of how it can be used by the browser in URLs and in scripting. Next, you will use the class attribute to refactor the code from this section to apply colors to the content with new classes.
If you don't care about the ordering of child elements, you can use an attribute selector in selenium to choose elements based on any attribute value. A good example would be choosing the 'username' element of the form above without adding a class. They're just so flexible when you need to match elements containing attributes with specific values. The most common child selector is the descendant selector, which matches every element that follows an identified ancestor. Descendant selectors are created by spacing apart elements within a selector, creating a new level of hierarchy for each element list. Structural pseudo-classes are advanced selectors that enable you to target specific elements based on their position in the document hierarchy.
These were introduced in CSS3, and they are built on selectors previously discussed, such as the adjacent sibling selector. In CSS, pattern matching rules determine which style rules apply to elements in the document tree. These patterns, called selectors, may range from simple element names to rich contextual patterns.
If all conditions in the pattern are true for a certain element, the selector matches the element. You have now set up the starting points for your index.html and your styles.css. In the next section, you will add an id attribute to elements in the HTML and create id selectors in the CSS to apply styles to those elements. To start working with id, class, and attribute selectors, you will first set up the HTML and CSS code that you will work on through the rest of the tutorial. In this section, you will write out all the necessary HTML and some initial CSS styles that will handle layout and start the visual aesthetic.
Writing CSS selectors most often involves setting a condition and locating the element in the HTML that fulfills that condition as true. Besides matching an attribute with an existing attribute or a specific value, we can use other types of attribute selectors to achieve partial matching on the value of an attribute. These selectors can also be combined to match very specific elements. Some of the common selectors looked at early may also be defined as attribute selectors, in which an element is selected based upon its class or ID value. These class and ID attribute selectors are widely used and extremely powerful but only the beginning.
Other attribute selectors have emerged over the years, specifically taking a large leap forward with CSS3. Now elements can be selected based on whether an attribute is present and what its value may contain. Vue selectors allow selecting elements by their component name and property values.
The syntax is very similar to attribute selectors and supports all attribute selector operators. React selectors allow selecting elements by their component name and property values. The CSS attribute selectors provides an easy and powerful way to apply the styles on HTML elements based on the presence of a particular attribute or attribute value. The use case here is to select all bare links, in other words those links that do not have any CSS class applied. To select those elements, we need to use attribute selector twice, once assuming empty content and the other one assuming no attribute at all. To select elements without attribute we can use not selector extension while for empty attribute attribute just CSS attribute selector with empty value.
The attribute selector is useful for finding particular attributes in the HTML and applying styles to them. However, the attribute selector also has several ways to look for the value of an attribute. In this final section, you will use the attribute selector to look for matching value strings and apply styles that meet these specific conditions.
This section presented you with a way to string class values together to create more specific scenarios in which to apply styles. In the next section, you will learn how to find an element on the page based on any attribute type. You now know what selector you can use in which situation. Where to use the type of selectors, where to use combinators, where to use pseudo-elements and where you can use pseudo-elements. One of the latest specs changes introduced a new flag for attribute selectors, which allows us to make the matching case insensitive, by adding an i after our selector.
This is fairly well supported and works across all modern browsers, except IE11. The first attribute selector identifies an element based on whether it includes an attribute or not, regardless of any actual value. To select an element based on if an attribute is present or not, include the attribute name in square brackets, [], within a selector. The square brackets may or may not follow any qualifier such as an element type or class, all depending on the level of specificity desired. This selector matches any HTML element with a class attribute that contains space-separated values, one of which is warning. For example, it matches the elements having the class values warning, alert warning etc.
Matching takes place on attribute values in the document tree. Default attribute values may be defined in a DTD or elsewhere, but cannot always be selected by attribute selectors. Style sheets should be designed so that they work even if the default values are not included in the document tree. A selector consisting of a single simple selector matches any element satisfying its requirements. The CSS attribute selector matches elements based on the presence or value of a given attribute.
Save these change to your styles.css and return to your browser. Refresh index.html and the styles will remain unchanged. The refactor to the code didn't change the styles, but did change how the elements are selected.
The versatility of a class is that the styles can be used more than once and on different element types. Additionaly, these selectors will only return the first matching element, not all of them. Feed Creator then takes the text content of that element or an attribute value. These where introduced in CSS3 to add decoration to elements semantically correct. For instance adding a icon to a button without adding an empty 'i'-tag or adding targeting a placeholder element that is a invisible element belonging to the 'input'-element. You can see this selector as 'selecting a part of an element.' Normally you would create a new element to do this but now you can target it being part of its original element.
Like IDs, the class attribute is used to include additional names for all page elements which are meant to have the exact same style. In Heap, we use classes as part of the CSS selector to match the right element on the page. The notation above captures the element we are looking to target in our simple example, though a selector like this might easily match multiple elements on a more complex webpage. Let's get into how we can use attributes, including IDs and classes, to accurately capture the element we want on more complex pages.
For a more in-depth introduction to CSS selectors, see this page onHow CSS Selectors Work. All of the above examples of attribute selectors are case-sensitive. If we insert an i before the closing square brackets, we can switch on case-sensitive matching.
A CSS selector is a way to describe the location of one or more elements in an HTML page. It uses characteristics, such as IDs, classes, and other attributes, to create a breadcrumb trail to a certain element in the HTML tree. For a deeper dive into CSS selectors, check out How CSS Selectors Work. Knowing how to select children of an element is largely beneficial, and quite commonly seen.
However sibling elements, those elements that share a common parent, may also need to be selected. These sibling selections can be made by way of the general sibling and adjacent sibling selectors. Child selectors provide a way to select elements that fall within one another, thus making them children of their parent element. These selections can be made two different ways, using either descendant or direct child selectors.
Also note that you should not insert important information with CSS, because that content will be unavailable to assistive technologies. It will also be unavailable if a visitor chooses not to use the style sheet. The golden rule is that CSS rules are for styling; HTML is for displaying important content. Note that the last three listed above (called "user action pseudo-classes" — the first two are the link pseudo-classes) can be used to style the states of any element.
Descendant selectors express such a relationship in a pattern. A descendant selector is made up of two or more selectors separated bywhite space. A descendant selector of the form "A B" matches when an elementB is an arbitrary descendant of some ancestor element A. The class attribute is mostly used to point to a class in a style sheet.
However, it can also be used by a JavaScript (via the HTML DOM – ссылка) to make changes to HTML elements with a specified class. Be aware of the different attribute selectors available. CSS selectors in Selenium allow us to navigate lists with more finesse than the above methods. If we have a ul and we want to select its fourth li element without regard to any other elements, we should use nth-child or nth-of-type.
In straight CSS, that allows you to override behavior of certain elements; we can also use it to select those elements. A CSS Selector is a combination of an element selector and a value which identifies the web element within a web page. They are string representations of HTML tags, attributes, Id and Class. As such they are patterns that match against elements in a tree and are one of several technologies that can be used to select nodes in an XML document. Pseudo-classes are selectors that only select elements when they are in a specific state, such as when a user is hovering over something.
Heap uses attributes to map your site's data to access elements of a webpage. Common attributes that are used in Heap CSS selectors are tags, IDs, and classes. The next set of selectors are specialized structural selectors as they match specific child elements only. You can't pass expressions to them to modify their behavior. This matches the pseudo-element that comes after the second from the last list item inside the last unordered list.
