Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

JavaScript JavaScript Functions Arrow Functions Create Functions Using Arrow Syntax

What causes 'preview' of random number in console? At about 2:30 into the video.

When calling the getRandomNumber() function in the console there seems to be a 'preview' result prior to hitting enter. I noticed it in the video and was able to reproduce locally. Does anyone know what is happening here?

1 Answer

Steven Parker
Steven Parker
229,582 Points

That's a feature of the browser devtools called "Eager Evaluation". When you type an expression in the Console, the Console shows a preview of the result of that expression below your cursor. Of course, in this case since the result is random, the value will change when you finish the line and it re-evaluates it.

You can turn this feature off if you don't want it. Open the settings (gear icon) in the console and clear the checkbox labeled "Eager evaluation".

thanks, man!