Click to change css
Many people who have been exposed to HTML and CSS programming will use JavaScript to interact with web pages. Among them, click events are the most common interaction method. Through click events, we can operate on elements in the web page, such as changing the style of the element (CSS), or triggering certain functions. Next, let's take a look at how to change CSS through click events.
1. Basic knowledge of HTML and CSS
Before understanding how click events change CSS, we need to master the basic knowledge of HTML and CSS. HTML is a markup language mainly used to create web pages. It consists of a series of tags (Tags). Tags wrap various elements in web pages, such as text, images, links, etc. For example, the following HTML code:
<!DOCTYPE html>
<html>
<head>
<title>我的网页</title>
<style>
h1 {
color: red;
}
</style>
</head>
<body>
<h1>欢迎来到我的网页</h1>
</body>
</html>In the above code, <!DOCTYPE html> declares the file type as HTML, <html> wraps the entire For web pages, the <head> tag contains some metadata of the web page, such as title, style, etc. The <title> tag defines the title of the web page, and the <style> tag defines the style of the h1 element (the font color is red). The <body> tag contains the main content of the webpage, including a <h1> tag, which displays the text "Welcome to my webpage".
CSS (Cascading Style Sheets) is a style sheet language, mainly used to define and control the styles of various elements in HTML. We can write CSS code in the <style> tag in the head of the HTML document, or we can write the style code into an external CSS file. In the above code, we have used internal styles to define the font color of the h1 element.
2. Basic knowledge of click events
Click events are one of the most commonly used interaction methods in JavaScript. When a user clicks on an element on a web page, the element will trigger a "click event", and then we can process the element by writing JavaScript code. The following is a simple sample code:
<!DOCTYPE html>
<html>
<head>
<title>我的网页</title>
<style>
h1 {
color: red;
cursor: pointer;
}
</style>
<script>
function changeColor() {
document.getElementsByTagName("h1")[0].style.color = "blue";
}
</script>
</head>
<body>
<h1 onclick="changeColor()">点击我改变颜色</h1>
</body>
</html>In the above code, we first add a cursor: pointer style to the h1 element, so that when the mouse is hovering over the h1 element It will turn into a hand shape, prompting the user to click on the element. Subsequently, a function named changeColor() was written in the <script> tag. The function of this function is to change the font color of the h1 element to blue. Finally, the onclick attribute is added to the <h1> tag. The value of this attribute is the changeColor() function we just defined, so click on the h1 element When the changeColor() function is triggered, the function of changing the color is realized.
3. Change CSS through click events
Through the above sample code, we can see that HTML elements can be operated through JavaScript click events, such as changing styles. Here is another example code for changing CSS through click events:
<!DOCTYPE html>
<html>
<head>
<title>我的网页</title>
<style>
h1 {
color: red;
cursor: pointer;
}
.changeColor {
color: blue;
}
</style>
<script>
function addClass() {
document.getElementsByTagName("h1")[0].classList.add("changeColor");
}
function removeClass() {
document.getElementsByTagName("h1")[0].classList.remove("changeColor");
}
</script>
</head>
<body>
<h1 onclick="addClass()">点击变蓝</h1>
<h1 onclick="removeClass()">点击变红</h1>
</body>
</html>In the above code, we first define two styles, one is the initial style of the h1 element, and the other is when the h1 element is clicked The style after, where .changeColor is a class selector used to add and remove styles of h1 elements. Subsequently, we defined two functions addClass() and removeClass(), which are used to add and delete the styles of h1 elements respectively. In the <body> tag, we added two h1 elements respectively, and bound addClass() and removeClass to the onclick attribute () function realizes the effect of clicking to change the style of h1 element.
Summary:
Through the above example code, we can learn how to change CSS through click events to achieve interactive effects on web pages. Of course, this is just a basic operation. In fact, more complex interactive effects can be achieved through JavaScript. Therefore, we need to continue to learn and master more JavaScript skills and knowledge in order to better achieve web page interaction effects.
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