TL;DR: Don't use nested IFs or nested ternaries

Problems

• Readability

• Default Case

Solutions

1. Rewrite the code as an IF condition with an early return

Context

Nesting is always a problem with complexity.

We can fix it with polymorphism or early returns

Sample Code

Wrong

const getUnits = secs => (
 secs <= 60       ? 'seconds' :
 secs <= 3600     ? 'minutes' :
 secs <= 86400    ? 'hours'   :
 secs <= 2592000  ? 'days'    :
 secs <= 31536000 ? 'months'  :
                    'years' 
)

Right

const getUnits = secs => {
 if (secs <= 60) return 'seconds'; 
 if (secs <= 3_600) return 'minutes'; 
 if (secs <= 86_400) return 'hours';   
 if (secs <= 2_592_000) return 'days';    
 if (secs <= 31_536_000) return 'months';  
 return 'years' 
}

// More declarative

const getUnits = secs => {
 if (secs <= 60) return 'seconds'; 
 if (secs <= 60 * 60) return 'minutes'; 
 if (secs <= 24 * 60 * 60) return 'hours';   
 if (secs <= 30 * 24 * 60 * 60) return 'days';    
 if (secs <= 12 * 30 * 24 * 60 * 60) return 'months';  
 return 'years' 
}

Detection

[X] Automatic

Linters can detect this complexity using parsing trees.

Tags

• IFs

Conclusion

We must deal with accidental complexity to improve code readability.

Relations

Disclaimer

Code Smells are my opinion.

Credits

Photo by NIKHIL on Unsplash

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One of the best things to come out of the home computer revolution could be the general and widespread understanding of how severely limited logic really is.

Frank Herbert

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This article is part of the CodeSmell Series.