How to use JavaScript in HTML

In Web development, HTML and JavaScript are two indispensable and important technologies. HTML is a markup language used to build web pages, while JavaScript is a scripting language used to add various interactive effects to web pages. The combination of HTML and JavaScript can realize colorful web applications and dynamic effects. This article will introduce how HTML uses JavaScript to implement various functions.

1. Insert JavaScript code

In HTML pages, you can use the tag to insert JavaScript code. The specific format is as follows:

Insert JavaScript into HTML Hello World! alert('Hello JavaScript!'); In the above code, use The tag inserts a piece of JavaScript code into the HTML document, and the alert() function pops up a warning box that displays "Hello JavaScript!". In this way, JavaScript code can be directly embedded in the page to implement various logical functions.

2. Event processing functions

In HTML, JavaScript can be used to implement various event processing functions, such as mouse click, mouse movement, page loading, etc. The following takes the mouse click event as an example to introduce how to use JavaScript to implement event processing functions.

Mouse click event with JavaScript Click me! In the above code, use the onclick attribute to implement the mouse click event handler function of the button. When the user clicks the button, a warning box will pop up and display "Hello JavaScript!". This method can be used to implement various mouse events, keyboard events, etc.

3. DOM operations

In HTML, JavaScript can be used to operate the DOM of the page, such as changing the style of elements, inserting, deleting elements, etc. The following takes inserting elements as an example to introduce how to use JavaScript to implement DOM operations.

Insert element with JavaScript Hello World! Add element Remove element function add() { var p = document.createElement('p'); var text = document.createTextNode('This is a new paragraph.'); p.appendChild(text); document.body.appendChild(p); } function remove() { var p = document.getElementsByTagName('p')[0]; p.parentNode.removeChild(p); } In the above code, use the createElement() method to create a new element, use the createTextNode() method to create a text node, and add the text node to the element, and finally Use the appendChild() method to add the element to the body element.

4. Form data processing

In HTML, JavaScript can be used to process form data, such as verifying user input data, updating data in real time, etc. The following takes verification of form data as an example to introduce how to use JavaScript to process form data.

Form validation with JavaScript function validateForm() { var x = document.forms["myForm"]["fname"].value; if (x == "") { alert("First name must be filled out"); return false; } } First name: In the above code, use the validateForm() function to verify the data entered by the user. If the user does not fill in the First name, a warning box will pop up to display an error message and prevent form submission. This method can perform various operations on form data, such as verifying data, updating pages in real time, etc.

Summary

This article introduces how HTML uses JavaScript to implement various functions, including inserting JavaScript code, event handling functions, DOM operations, form data processing, etc. By understanding these basics, you can provide more powerful tools and more flexible operations for web development.