Javascript - predict operation result

github logo ・1 min read

Sorry for this may be well-known for some people, especially professional JS devs. But JS is so widely used in projects that I expect some others (like me) may find some results surprising.

Predict (try) result of operations (including type!) of few following expressions - and then check yourself (e.g. in browser console).

  1. "5" + 3
  2. "5" - 3
  3. [] + 2
  4. {} + 2
  5. [] - 2
  6. {} - 2
  7. [] + 2 == 2 + []
  8. {} + 2 == 2 + {}
  9. {} + []
  10. [] + {}

Post in the comment, well... No answers (everyone can check)... Post how many you've guessed. And which is the most confusing in your opinion.

Few are obvious so hopefully your result would be non-zero. No sense to cheat, we are not in interview or exam - just have fun! :)

twitter logo DISCUSS (4)
markdown guide

A little late to the party!

Surprisingly, I couldn't successfully guess the third one and the last three. JavaScript is really a weird language haha!

This is astonishing knowing that a language that can interpret these instructions is ruling the Web...


I couldn't successfully guess the third one and the last three

Oh, that's cool! I couldn't guess almost all of them. However I'm more backend developer and use JS occasionally. Nevertheless it is funny that people blame PHP for being illogical when there is JS :)


That's why I am loving developing applications using Elm. It is a language that has all the necessary tools to build modern websites as well as web applications or even progressive web apps.

It is really shrunk down to the core utilities and has types which means it is safer to use than JavaScript.

I wish types were more of a thing in PHP but its already really good at the moment, especially with the 7.4 release of PHP.

using Elm

thanks for this hint - as I'm not neck-deep in front-end, I often miss new trends, so I'll look into this :)

However I know that often languages are chosen not because of their specific properties, but because of "social" consideration - including how many people use it, how many support and how hard it could be to hire programmers for it etc :)

Classic DEV Post from Jul 14 '17

Developer under time pressure ? work faster : work better

Wrong choices you can make under time pressure.

Rodion Gorkovenko profile image
Developer, Dreamer, School-Teacher, author of CodeAbbey and few other silly projects :)