Page 185 - JavaScript

Chapter 20: Comments

Syntax

• // Single line comment (continues until line break)
• /* Multi line comment */
• <!-- Single line comment starting with the opening HTML comment segment "<!--" (continues
until line break)
• --> Single line comment starting with the closing HTML comment segment "-->" (continues
until line break)

Examples

Using Comments

To add annotations, hints, or exclude some code from being executed JavaScript provides two
ways of commenting code lines

Single line Comment //

Everything after the // until the end of the line is excluded from execution.

function elementAt( event ) {
// Gets the element from Event coordinates
return document.elementFromPoint(event.clientX, event.clientY);
}
// TODO: write more cool stuff!

Multi-line Comment /**/

Everything between the opening /* and the closing */ is excluded from execution, even if the
opening and closing are on different lines.

/*
Gets the element from Event coordinates.
Use like:
var clickedEl = someEl.addEventListener("click", elementAt, false);
*/
function elementAt( event ) {
return document.elementFromPoint(event.clientX, event.clientY);
}
/* TODO: write more useful comments! */

Using HTML comments in JavaScript (Bad practice)

HTML comments (optionally preceded by whitespace) will cause code (on the same line) to be

https://riptutorial.com/ 142