How to comment js code

JavaScript comments are used to explain JavaScript code and enhance its readability.

JavaScript comments can also be used to prevent execution when testing alternative code.

Single-line comments

Single-line comments start with //.

Any text between // and the end of the line will be ignored by JavaScript (will not be executed).

This example uses a single-line comment before each line of code:

// 改变标题：
 document.getElementById("myH").innerHTML = "我的第一张页面";
// 改变段落：
 document.getElementById("myP").innerHTML = "我的第一个段落。";

本例在每行结尾处使用了单行注释来解释代码：
var x = 5;      // 声明 x，为其赋值 5
var y = x + 2;  // 声明 y，为其赋值 x + 2

Multi-line comments

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

Any text between /* and */ will be ignored by JavaScript.

This example uses multi-line comments (comment blocks) to explain the code:

/*
 下面的代码会改变
 网页中
 id = "myH" 的标题
 以及 id = "myP" 的段落：
*/
document.getElementById("myH").innerHTML = "我的第一张页面";
document.getElementById("myP").innerHTML = "我的第一个段落。";

Comments: It is most common to use single-line comments.

Tip: Comment blocks are often used for official statements.

Use comments to prevent execution

Using comments to prevent code execution is great for code testing.

Adding // before a line of code will change the executable line of code to a comment.

This example uses // to prevent the execution of a line of code:

//document.getElementById("myH").innerHTML = "我的第一张页面";
document.getElementById("myP").innerHTML = "我的第一个段落。";

This example uses a comment block to prevent the execution of multiple lines of code:

/*
document.getElementById("myH").innerHTML = "我的第一张页面";
document.getElementById("myP").innerHTML = "我的第一个段落。";
*/

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