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Comments in JavaScript – Tutorial

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Comments in JavaScript - Tutorial: A picture describing the use of single-line comments in JavaScript.

Comments in JavaScript: Overview

            Comments in JavaScript are primarily used to explain what the code is for or to make it more readable. Single line comments start with a double forward slash (//), but do not have an end tag. Any text that is written after (//) will be completely ignored by JavaScript and will not be executed or displayed by the browser.

Start “Tag”:  //
End “Tag”: None
Example:  // Write to element with ID of “line”.

document.getElementById(“line”).innerHTML=”Are you sure?“;

Explanation: Labels JavaScript code so anyone viewing will know the statement is to write to an element with an ID of “line”.

Comments in JavaScript - Tutorial: A picture describing the use of single-line comments in JavaScript.

Comments in JavaScript – Tutorial: A picture describing the use of single-line comments in JavaScript.

            Multi-line comments in JavaScript start with a forward slash and an asterisk (/*) and end with an asterisk and a forward slash (*/). This allows for breaking your comments up into many lines, making it more readable for later editing. Just like single line comments, multi-line comments are ignored by JavaScript and will not be displayed by browsers.

Start “Tag”:  /*
End “Tag”:  */
Example: /*

This is an

Example of a

Multi-line comment.

*/

Explanation: Allows you to write comments across multiple lines that will be ignored by JavaScript and web browsers.

Comments in JavaScript: Instructions

  1. To add a single line comment, type: //
  2. On the same line enter the information you want as your comment.
  3. To add multi-line comments on the line you want your comment to start, type: /*
  4. On a new line start the comment you want to enter
  5. When your comment is complete, type: */

Comments in JavaScript: Video Lessons

            The following video lessons, titled “Single-line Comments” and “Multi-line Comments,” show you how to create comments in JavaScript. The following video lessons are from our Introductory JavaScript course, titled “Mastering Introductory JavaScript Made Easy v.1.0.”

 

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