Code Smell 69 — Big Bang (JavaScript Ridiculous Castings)

This handy operator is a troublemaker.

Photo by Greg Rakozy on Unsplash

TL;DR: Don’t mix booleans with non-booleans.

Problems

• Not Declarative Code
• Hard to debug
• Magic Castings
• Accidental Complexity

Solutions

1. Be Explicit
2. Don’t mix Booleans with non-booleans.
3. Fail Fast
4. Be Smarter than your compiler.
5. Stay loyal to the bijection.

The one and only software design principle

Sample Code

Wrong

Right

Detection

Since this is a “feature” in some languages it would be hard to test. We can set programming policies or choose more strict languages.

We should detect ! !! usages in non-boolean objects and warn our programmers.

Tags

• Casting
• Coercion
• Javascript

Conclusion

Languages like JavaScript divide their whole universe into true or false values. This decision hides errors when dealing with non booleans.

We should be very strict and keep booleans (and their behavior), far away from non booleans.

Relations

Code Smell 24 — Boolean Coercions

Code Smell 06 — Too Clever Programmer

More info

The Double-Bang (!!) Operator And A Misunderstanding Of How JavaScript Handles Truthy / Falsy…

Truthy

It is easier to write an incorrect program than understand a correct one.

Alan J Perlis

Software Engineering Great Quotes

This article is part of the CodeSmell Series.

How to Find the Stinky parts of your Code