How css and js

Use together to achieve web page interaction effects

Web technology is constantly developing and has become an indispensable part of people's lives and work. Among them, CSS and JavaScript are two very important technologies. CSS (Cascading Style Sheets) can control the layout and style of web pages, while JavaScript can achieve interactive and dynamic effects on web pages. When developing web pages, you often need to use CSS and JavaScript together. Next, this article will discuss how to use CSS and JavaScript to achieve interactive effects on web pages.

1. The relationship between CSS and JavaScript

Let’s first talk about the relationship between CSS and JavaScript. Both CSS and JavaScript can be used to control the appearance and behavior of web pages, but they execute at different times. The main function of CSS is to control the style and layout of web pages. It is a passive technology and its execution time is when the web page is loaded. JavaScript is an active technology that can achieve interactive and dynamic effects, and can also control the style and layout of web pages. JavaScript is executed after the web page is loaded and the corresponding code is executed when the user interacts.

In practical applications, CSS is usually used to control the layout and basic style of the web page, and then JavaScript is used to achieve the interactive and dynamic effects of the web page.

2. Use CSS and JavaScript to achieve web page effects

Now, let’s look at a few examples of using CSS and JavaScript to achieve web page interactive effects.

1. Change the element style when the mouse hovers over it

This is a relatively simple interactive effect. When the mouse hovers over an element, change its style. For example, when the mouse is hovering over a link, change its color or add styles such as underlining.

This effect can be achieved using the CSS :hover pseudo-class. For example, the following code changes the color of a link when the mouse is hovering over it:

a:hover {
    color: red;
}

If you want to achieve more complex changes, you can use it with JavaScript. For example, you need to display a drop-down menu when the mouse hovers over an element. You can define the style of the drop-down menu in CSS, and then use JavaScript to control showing and hiding.

2. Click the button to switch the element state

This is a common interaction effect. When the user clicks a button, the element state is switched. For example, clicking a button expands or collapses an accordion, or shows or hides an element.

This effect can be achieved using JavaScript. For example, the following code can toggle the display and hiding of an element:

<button onclick="toggle()">Toggle</button>
<div id="content">Hello world!</div>
<script>
function toggle() {
  var content = document.getElementById("content");
  if (content.style.display == "none") {
    content.style.display = "block";
  } else {
    content.style.display = "none";
  }
}
</script>

When the button is clicked, the toggle() function is called to toggle the display and hiding of the element. Document.getElementById() is used here to obtain the element, and then modify its style to display and hide it.

3. Drag the element and change the position

This is a relatively complex interactive effect. When the user drags an element, its position is changed. This effect can be achieved using the new drag and drop API in HTML5.

For example, the following code can achieve the effect of dragging an element:

<div id="drag" draggable="true">Drag me</div>
<script>
var drag = document.getElementById("drag");
drag.addEventListener('dragstart', function(event) {
  event.dataTransfer.setData("text/plain", event.target.id);
});
document.addEventListener('dragover', function(event) {
  event.preventDefault();
});
document.addEventListener('drop', function(event) {
  var id = event.dataTransfer.getData("text");
  var element = document.getElementById(id);
  element.style.left = event.clientX + "px";
  element.style.top = event.clientY + "px";
  event.preventDefault();
});
</script>

In this code, first set the draggable attribute to true to set the element to be draggable. Then, when dragging begins, the data is transferred by calling the event.dataTransfer.setData() method. During the dragging process, prevent the default behavior by listening to the dragover event, then obtain the transmitted data in the drop event, and then modify the element's style to change the position.

3. Summary

CSS and JavaScript are both important technologies in web development. In practical applications, they need to be used simultaneously to achieve interactive and dynamic effects on web pages. CSS is responsible for controlling the style and layout of web pages, and JavaScript is responsible for achieving interactive and dynamic effects. Proper use of CSS and JavaScript can provide users with a better user experience and improve the user experience and usability of the website.

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