How to write and execute code using JavaScript in web pages

In web design and development, JavaScript is a very important programming language. The breadth of JavaScript is mainly reflected in server-side JavaScript, client-side JavaScript, Node.js, etc. Among them, client-side JavaScript is most widely used in various web applications (Web App). Therefore, we need to understand how to write and execute code using JavaScript in web pages.

The earliest application of JavaScript is to embed scripts in HTML pages, that is, internal JavaScript. This method is not only easy to learn, but writing JavaScript code directly in the HTML page allows us to build interactive JavaScript effects faster. This article will introduce the use of internal JavaScript.

Introducing JavaScript code To use internal JavaScript in HTML pages, we first need to introduce JavaScript scripts into the HTML code. The specific method is to add a element to the HTML page, and at the same time reference the file address where the JavaScript code is stored in the src attribute of the element (if the JavaScript code is written directly in the HTML file, the src attribute can be omitted). As shown below, we name the imported JavaScript file "script.js":

内部JavaScript示例 内部JavaScript示例 Add JavaScript code to the HTML page In the ## of the HTML file In #```` , write JavaScript code directly within the element. As shown in the example below, we can add a button element, and whenever the user clicks the button, the text message "Hello World!" will be displayed on the web page.

内部JavaScript示例 内部JavaScript示例 点击以下按钮：

点我 Here we use the onclick event to listen to the button click event and pop up a message box when the event is triggered. The alert() method is one of the native methods provided by JavaScript, which is used to pop up a message box in the browser. Using this method, we can quickly and easily add some short JavaScript code to the web page.

Add code in JavaScript file In addition to adding JavaScript code to the HTML page, we can also store the JavaScript code separately in an external file, named as "script.js" and then introduce the file in the HTML page. As shown below:

HTML file:

内部JavaScript示例 内部JavaScript示例 点我 JavaScript file (script.js):

function clickBtn() { alert("Hello World!"); } When the user clicks the button, the clickBtn() function will be executed. JavaScript code and pops up a message box in the browser.

The advantage of using external JavaScript files is that reused JavaScript codes can be saved into separate files, which significantly improves the reusability of the code. At the same time, external JavaScript files can also be referenced by multiple HTML pages, greatly improving development efficiency.

Summary

Internal JavaScript is a method of embedding JavaScript script code in HTML pages. Using this method, we can quickly and easily add JavaScript effects to web pages. In this way, we can write JavaScript code directly in the HTML file through the element. At the same time, we can also store the JavaScript code separately in an external file and use the JavaScript code by introducing the file into the HTML page.

Either way, with internal JavaScript we can bring endless possibilities to web applications.