JavaScript (JS) is a popular programming language used for building web applications. While CSS, also known as CSS3, is a style sheet language used to style web pages and web applications. In order to style a web page, it is necessary to have a reference to the CSS class名.

JavaScript can be used to style web pages using CSS classes. For example, if you want to style a web page to have a red background, you can create a CSS class that specifies the color and add this class to the HTML element that you want to style. Then, in JavaScript, you can use the `style.backgroundColor` property to set the background color of the element.

Another example is to style a list of items, you can create a CSS class that specifies the item style, for example, the text style, the font style, the background color, and the border style, and then add this class to the list element. In JavaScript, you can use the `li.itemStyle` property to style the list items.

In addition to this, JavaScript can also be used to style web pages using tables, by creating a table and adding a class to the table cell, you can use the `style.color` property to set the color of the cell, or you can use the `style.font-size` property to set the font size of the cell.

In conclusion, JavaScript and CSS are two powerful tools used to style web pages. By using JavaScript and CSS, we can create more beautiful and user-friendly web pages and web applications.