JavaScript Comments

JavaScript comments can be used to make the code more readable.

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JavaScript Comments

Comments will not be executed by JavaScript.

Comments can be added to explain the JavaScript, or to make the code more readable.

Single line comments start with //.

The following example uses single line comments to explain the code:

Example

// Write to a heading:
document.getElementById("myH1").innerHTML="Welcome to my Homepage";
// Write to a paragraph:
document.getElementById("myP").innerHTML="This is my first paragraph.";

Try it yourself »

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JavaScript Multi-Line Comments

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

The following example uses a multi line comment to explain the code:

Example

/*
The code below will write
to a heading and to a paragraph,
and will represent the start of
my homepage:
*/
document.getElementById("myH1").innerHTML="Welcome to my Homepage";
document.getElementById("myP").innerHTML="This is my first paragraph.";

Try it yourself »

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Using Comments to Prevent Execution

In the following example the comment is used to prevent the execution of one of the codelines (can be suitable for debugging):

Example

//document.getElementById("myH1").innerHTML="Welcome to my Homepage";
document.getElementById("myP").innerHTML="This is my first paragraph.";

Try it yourself »

In the following example the comment is used to prevent the execution of a code block (can be suitable for debugging):

Example

/*
document.getElementById("myH1").innerHTML="Welcome to my Homepage";
document.getElementById("myP").innerHTML="This is my first paragraph.";
*/

Try it yourself »

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Using Comments at the End of a Line

In the following example the comment is placed at the end of a code line:

Example

var x=5; // declare a variable and assign a value to it
x=x+2; // Add 2 to the variable x

Try it yourself »