What does "side effect" mean in programming?
side effect is one of the most common terms in software development. This guide explains what it means, how it is used in practice, and why it matters, with real examples from the developer world.
Definition
Any operation a function performs beyond returning a value: writing to a database, modifying a variable outside its scope, logging to the console, or making a network request. Side effects make code harder to test and reason about. Functional programming aims to isolate side effects.
Example
"That function has a side effect: it modifies the global config object. That is why the test environment is leaking state."
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