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Master the syntax of id selector

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Release： 2024-01-03 15:18:48

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Master the syntax of id selector

To learn how to use the syntax of the id selector, you need specific code examples

When learning CSS (cascading style sheets), understand and master the syntax and use of the selector Method is very important. Among them, the id selector is a commonly used selector that allows us to select specific elements and apply styles to them by adding the id attribute to HTML elements.

First, let us understand the syntax of the id selector. In CSS, when using the id selector, you need to add the pound sign "#" in front of the selector, followed by the id name. For example, if our HTML element sets the id attribute to "my-element", then the corresponding CSS selector is "#my-element".

Next, we use some specific code examples to demonstrate the use of the id selector.

HTML代码：
<!DOCTYPE html>
<html>
<head>
    <style>
        /* 使用id选择器设置特定元素的样式 */
        #my-element {
            color: red;
            font-weight: bold;
        }
    </style>
</head>
<body>
    <div id="my-element">
        这是一个特定元素
    </div>
    <p>
        这是普通文本。
    </p>
</body>
</html>

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In the above code, we defined an id selector #my-element within the <style> tag, and set some style attributes ( If the color is red, the font will be bold). Next, within the <body> tag, we pass the <div> element and set the id attribute to "my-element". In this way, the element is selected and the style we defined is applied.

It is worth noting that the id selector is a unique selector, that is, the id attribute in each HTML document should be unique. If multiple elements have the same id, only the first element will be styled, and subsequent ones will be ignored.

In addition to using the id selector directly in CSS code, we can also dynamically change the style of elements through scripting languages such as JavaScript. Below is a simple JavaScript example demonstrating how to use the id selector.

JavaScript代码：
var myElement = document.getElementById("my-element");
myElement.style.backgroundColor = "yellow";

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In the above code, we use JavaScript's getElementById method to get a specific element by passing in the id name. We can then dynamically change the background color of that element to yellow by setting the style.backgroundColor property.

To sum up, learning the syntax and usage of the id selector is an important step in getting started with CSS. By adding id attributes to HTML elements and using id selectors for style settings, we can precisely control specific elements to meet our web page style requirements. At the same time, we can also use scripting languages such as JavaScript to dynamically change the style of elements to increase the interactivity and dynamics of the page.

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