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The use of || operator in assignments

See original GitHub issue

In the topic 15.7 this kind of assignment is favored over ternaries: const foo = a || b;. Actually, this pattern is used in a lot of the examples, but should it be discouraged since it can produce undesired behavior when the left operand is falsy? In the above example if a is falsy so b would be the result.

I know the developer should distinguish problematic cases, but one of the goals of the style guide is to avoid potential issues.

Issue Analytics

State:
Created 7 years ago
Comments:8 (3 by maintainers)

Top GitHub Comments

2reactions

getifycommented, Aug 7, 2016

Just FYI: technically the a || b and a ? a : b are not strictly equivalent (but very close). When the a expression is something more than an identifier (an object prop access, a function, etc), if evaluating that expression has side effects, the outcomes will be different in the two cases. a || b evaluates a only once, and a ? a : b evaluates a twice.

1reaction

felipethomecommented, Aug 3, 2016

Actually, it seems 7.7 already explains that in the comments of the example. Maybe the content of the comment presented as a Why? quote would be more effective?