How to add comments in JavaScript

How to add comments in JavaScript: 1. Use the "//" symbol to make a single-line comment. Any text between "//" and the end of the line will be ignored by JavaScript; 2. Use the "/*" symbol to comment. ” and end with “*/” to implement multi-line comments.

The operating environment of this article: windows7 system, javascript version 1.8.5, Dell G3 computer.

JavaScript Comments

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:

Example

// 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。";

This example uses a single-line comment at the end of each line to explain the code:

Example

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 */.

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

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

Example

/*
 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 lines of code:

Example

//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 comment blocks to prevent the execution of multiple lines of code:

Example

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

Recommended study: "javascript advanced tutorial"

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