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Cover image for Code Smell 156 - Implicit Else
Maxi Contieri
Maxi Contieri

Posted on • Originally published at maximilianocontieri.com

Code Smell 156 - Implicit Else

#javascript #webdev #beginners #programming

We learn if/else on our first programming day. Then we forget the else

TL;DR: Be explicit. Even with Else.

Problems

Solutions

  1. Write the explicit else

Context

If we early return on an IF sentence we can omit the else part.

Afterward, we Remove the IF and use polymorphism.

That is when we miss the real cases.

Sample Code

Wrong 

function carBrandImplicit(model) {
  if (model === 'A4') {
    return 'audi';
  }
  return 'Mercedes-Benz';
}
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Right 

function carBrandExplicit(model) {
  if (model === 'A4') {
    return 'audi';
  }
  if (model === 'AMG') {
    return 'Mercedes-Benz';
  }

  // Fail Fast
  throw new Exception('Model not found);
}
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Detection

[X] Automatic

We can check syntax trees and parse them and warn for missing else.

We can also rewrite them and perform mutation testing.

Tags

  • Conditionals

Conclusion

This kind of smell brings a lot of public debate, and hate.

We must exchange opinions and value each pros and cons.

Relations

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More Info

Stop Using Implicit Else

When To Use Implicit Else

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Fail Fast

Maxi Contieri ・ Dec 6 '20 ・ 6 min read

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How to Get Rid of Annoying IFs Forever

Maxi Contieri ・ Nov 9 '20 ・ 5 min read

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Credits

Photo by Elena Mozhvilo on Unsplash

The biggest issue on software teams is making sure everyone understands what everyone else is doing.

Martin Fowler

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Software Engineering Great Quotes

Maxi Contieri ・ Dec 28 '20 ・ 13 min read

#codenewbie #programming #quotes #software

This article is part of the CodeSmell Series.

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How to Find the Stinky parts of your Code

Maxi Contieri ・ May 21 '21 ・ 7 min read

#codenewbie #tutorial #codequality #beginners

Top comments (4)

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lukeshiru profile image
Luke Shiru •

You really think throwing is preferable over an actual default case? From my point of view that second snippet is way more smellier than the first one. Having to wrap it on a try/catch in order to be "safe" makes it usage way less convenient.

My suggestion would be to just have something simple like this (added JSDocs to make DX even better):

const modelBrandMap = /** @type {const} */ ({
    A4: "Audi",
    AMG: "Mercedes-Benz",
});

/**
 * @template {keyof typeof modelBrandMap} Model
 * @param {Model} model
 */
const carBrand = model => modelBrandMap[model];
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And then the usage is as simple as:

// We can graceful default the brand to "Unknown":

console.log(`The brand for "${model}" is "${carBrand(model) ?? "Unknown"}".`);

// Or if you prefer to show an error, you can always:

const brand = carBrand(model);

brand
    ? console.log(`The brand for "${model}" is "${brand}"`)
    : console.error(`There's no brand for "${model}"`);

// Or maybe using if:

const brand = carBrand(model);

if (brand) {
    console.log(`The brand for "${model}" is "${brand}"`);
} else {
    console.error(`There's no brand for "${model}"`);
}
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As you can see, we have several options, none of which will make the app explode for not finding a result. Now with your approach we have less options and we need to use more boilerplate:

// The graceful approach:

try {
    console.log(`The brand for "${model}" is "${carBrandExplicit(model)}".`