This article brings you relevant knowledge about javascript. In JavaScript, unlike languages such as Java, it does not have any printing or output methods. There are 4 ways to use it in js To output data, this article will introduce it to you in detail through example code. I hope it will be helpful to you.
[Related recommendations: javascript video tutorial, web front-end】
Preface
In JavaScript, unlike languages such as Java, it does not have any printing or output methods. The following four methods are usually used to output data.
- Use
window.alert()to pop up the warning box - Use
document.write()to write the content to HTML In the document - Use
innerHTMLto write to the HTML element - Use
console.log()to write to the browser console
They are used below to show an example.
window.alert()
Create a new HTML file, and then use VSCode to write the following code.
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>window.alert()</title>
</head>
<body>
<p>弹窗显示</p>
<script type="text/javascript">
window.alert("这是一条弹窗测试！");
</script>
</body>
</html>Then open the above file with a browser. When it is opened, the following pop-up window will be displayed. After clicking OK, the pop-up window will close and the content will be displayed on the web page.
document.write()
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>document.write()</title>
</head>
<body>
<p>写入 HTML 文档</p>
<script type="text/javascript">
document.write(Date());
</script>
</body>
</html>After creating a new HTML file and writing the above content, the browser will open and the page will display the following content, as you can see Using document.write() to write the current time is successful. However, it should be noted that if document.write() is loaded at the same time as other content before the content is loaded, it can be displayed together with other content. However, if document.write() is executed after the page content has been loaded, all the previously loaded content will be overwritten by the written content.
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>document.write()</title>
</head>
<body>
<p>写入 HTML 文档</p>
<button onclick="showDate()">展示时间</button>
<script type="text/javascript">
function showDate() {
document.write(Date());
}
</script>
</body>
</html>The following is the execution of document.write() after the page is loaded. Comparison before and after, indicating that it is called after the page is loaded. document.write() will overwrite the previous page content.
before and after
document.getElementById(id) method, and then you can use innerHTML to get or insert element content.
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>innerHTML</title>
</head>
<body>
<p id="inner">操纵 HTML 元素</p>
<button onclick="changeContext()">点击修改上述内容</button>
<script type="text/javascript">
function changeContext() {
document.getElementById("inner").innerHTML = "修改后的内容";
}
</script>
</body>
</html>Before modification After modification
##console.log()
To use
console.log() method requires our browser to support debugging. Chrome is generally recommended. Then use the F12 shortcut key to open debugging mode and switch to the Console menu in the debugging window. Because I am using Edge here, the console is displayed. This choice of browser is mainly based on your own preferences, but Chrome is generally recommended. <pre class='brush:php;toolbar:false;'><!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>console.log</title>
</head>
<body>
<p>浏览器调试模式查看</p>
<script type="text/javascript">
var num1 = 11;
var num2 = 10;
console.log(num1 + num2);
</script>
</body>
</html></pre>
Summary
The above is about the output in JavaScript, although it is not as similar as Java.
System.out.println( ) method to print and output, but using the above 4 methods can basically meet the needs of daily development. 【Related recommendations:
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