What does javascript:; mean when it appears on a web page?

In our daily web browsing, we often see link addresses similar to javascript:; appearing on web pages, but many people don’t know what it means and how to understand it.

First of all, we need to understand what JavaScript is. JavaScript is a dynamic programming language mainly used to achieve dynamic interactive effects on web pages. Its main uses are twofold. One is as a client-side scripting language, providing the ability to dynamically interact with users, and is usually embedded in HTML code; the other is as a server-side scripting language, programming the server side. JavaScript has the characteristics of high development efficiency, easy to use, and wide application, so it is favored by developers.

So, when we see a link address like javascript:; appear on the page, what does it mean? In fact, this is a special URL protocol in JavaScript. When the href attribute of the link is javascript:;, the link will not perform any operation, and when you click it, the page will not jump to any other page or refresh the page, which is equivalent to an invalid link.

However, developers can control the behavior of this link through JavaScript code. For example, when the link is clicked, a modal box can pop up to prompt the user, or perform form verification, etc. Common JavaScript codes include pop-up windows, page scrolling, form validation, etc. These can be implemented by adding code after the javascript:; of the link.

For example, suppose we have a button. When clicking it, a modal box needs to pop up to prompt the user. We can write the code like this:

<button onclick="alert('Hello world!')">点击我弹出提示框</button>

The onclick event here can trigger the JavaScript code alert( 'Hello world!'), when the user clicks the button, a prompt box with the text "Hello world!" will appear.

Another example, when we need to scroll the page to a specified position, we can write JavaScript code like this:

<a href="javascript:scroll(0,500)">点击我滚动页面</a>

This link will scroll the page to the Y-axis coordinate of 500 on the page , achieving the effect of scrolling the page.

To sum up, the link address javascript:; is not a link without any effect. It represents a protocol that can be embedded with JavaScript code, which can be used to achieve rich dynamic effects and interactive experiences. But at the same time, it should be noted that non-standard and malicious JavaScript code may also bring bad experience and security risks to users. Therefore, developers need to be careful when writing JavaScript code to ensure its safety and reliability.

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