JavaScript comments

JavaScript comments can be used to improve the readability of your code.

JavaScript Comments

JavaScript will not execute comments.

We can add comments to explain JavaScript or improve the readability of the code.

Single-line comments begin with //.

This example uses a single line comment to explain the code:

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>php中文网(php.cn)</title>
</head>
<body>
<h1 id="myH1"></h1>
<p id="myP"></p>
<script>
    // 输出标题：
    document.getElementById("myH1").innerHTML="PHP中文网";
    // 输出段落：
    document.getElementById("myP").innerHTML="PHP.CN";
</script>
<p><b>注释：</b>注释不会被执行。</p>
</body>
</html>

Run the program and try it

JavaScript multi-line comments

Multi-line comments start with /* and end with */.

The following example uses multi-line comments to explain the code:

<!DOCTYPE html>
<html>
<head>
<title>php中文网测试实例</title>
<meta charset="utf-8">
</head>
<body>
<h1 id="myH1"></h1>
<p id="myP"></p>
<script>
/*
下面的这些代码会输出
一个标题和一个段落
并将代表主页的开始
*/
document.getElementById("myH1").innerHTML="欢迎来到php中文网";
document.getElementById("myP").innerHTML="这是一个段落。";
</script>
<p><b>注释：</b>注释块不会被执行。</p>
</body>
</html>

Run the program to try it

Use comments to block execution

In the following example, the comment is used to prevent the execution of one of the lines of code (can be used for debugging):

<!DOCTYPE html>
<html>
<head> 
<meta charset="utf-8"> 
<title>php中文网(php.cn)</title> 
</head>
<body>
<h1 id="myH1"></h1>
<p id="myP"></p>
<script>
//document.getElementById("myH1").innerHTML="欢迎来到我的主页";
document.getElementById("myP").innerHTML="这是我的第一个段落。";
</script>
<p><strong>注意:</strong> 注释块不会被执行</p>
</body>
</html>

Run the program to try it

Note : Multi-line comments are used the same as above. Just wrap the code blocks that do not need to be executed with multi-line comments.

Use comments at the end of the line

Like this

var x=5; // Declare x and assign 5 to it

Continuing Learning

new file

<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>php中文网(php.cn)</title> </head> <body> <h1 id="myH1"></h1> <p id="myP"></p> <script> // 输出标题： document.getElementById("myH1").innerHTML="PHP中文网"; // 输出段落： document.getElementById("myP").innerHTML="PHP.CN"; </script> <p><b>注释：</b>注释不会被执行。</p> </body> </html>

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Automatic operation

JavaScript comments

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