How does Javascript call css

With the rapid development of Internet technology, JavaScript, as a widely used scripting language, is often used for the interaction of web pages and the display of dynamic effects. CSS (Cascading Style Sheets) is a language used to describe the style and appearance of HTML documents. It can achieve better results in the layout and appearance of web pages. Therefore, the combined use of JavaScript and CSS allows us to achieve more flexible and diverse effects in web design and development. This article will focus on how JavaScript calls CSS to help you better use these two languages.

JavaScript method of calling CSS

1. Get the element object through getElementById(), and then change the CSS style by modifying the style attribute of the element object

In JavaScript There is a very important method getElementById(), which can get a specific element object on the page by specifying the id attribute. We can use this method to obtain the specific element object whose style needs to be modified, and then operate the style attribute of the element object to change the style of the element.

For example, we can change the font size of the element with the id "text" through the following code:

document.getElementById("text").style.fontSize="20px";

2. Use the setAttribute() method to modify the class attribute of the element object

In addition to changing the style of the element through the getElementById() method, we can also modify the class attribute of the element object through the setAttribute() method. Using the class attribute allows multiple elements to share the same style, reducing duplicate code.

For example, we can modify the class attribute value of the element with id "text" to "change" through the following code:

document.getElementById("text").setAttribute("class","change");

3. Use the getElementsByTagName() method to obtain a set of element objects , and then change the CSS style by modifying the className attribute of the element object.

getElementsByTagName() method can obtain the element object of the specified tag name, and returns a list containing all element objects under the tag name. We can use this method to obtain a set of element objects whose styles need to be modified, and then change the style of the elements by modifying the className attribute of the element objects.

For example, we can modify the class attribute value of all elements with the tag name "p" to "change" through the following code:

var paragraphs = document.getElementsByTagName("p");
for (var i = 0; i < paragraphs.length; i++) {
    paragraphs[i].className = "change";
}

Summary

The above is the JavaScript call CSS methods, through these methods we can use CSS styles in combination to achieve interactive and dynamic effects on web pages. It should be noted that when modifying CSS styles with JavaScript, it is best to avoid using inline style formulation. Instead, it should be done with the help of CSS class names, id and other attributes, which is more elegant and easier to maintain.

This article only introduces some common methods. If you want to learn more about the combination of JavaScript and CSS, you need to learn some more advanced knowledge, such as operating CSS styles through the jQuery library, or by specifying JavaScript events to dynamically modify CSS styles, etc. Strengthening the study of JavaScript and CSS can allow us to better display the appearance and user experience of the page when designing web pages.

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