JavaScript Comments - Commenting Code in JavaScript



JavaScript Comments

  • JavaScript comments can be used to explain JavaScript code, and to make it more readable.
  • 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 code line.
javascript-innerhtml

Sample Code

<!DOCTYPE html>
<html>
<body>

<h1 id="myH"></h1>
<p id="myP"></p>

<script>
// Change heading:
document.getElementById("myH").innerHTML = "Kaashiv infotech" ;
// Change paragraph:
document.getElementById("myP").innerHTML = "wikitechy";
</script>

</body>
</html>

Output

Kaashiv infotech
wikitechy

Multi-line Comments

  • Multi-line comments start with /* and end with */.
  • Any text between /* and */ will be ignored by JavaScript.
  • This example uses a multi-line comment (a comment block) to explain the code:
javascript-innerhtml-example

Sample Code

<!DOCTYPE html>
<html>
<body>

<h1 id="myH"></h1>
<p id="myP"></p>

<script>
/*
The code below will change
the heading with id = "myH"
and the paragraph with id = "myP"
*/
document.getElementById("myH").innerHTML = "JavaScript Comments";
document.getElementById("myP").innerHTML = "My first paragraph.";
</script>

</body>
</html>

Output

JavaScript Comments
My first paragraph.

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