Avoid Mutating Objects Loaded from JSON Files

Today I learned that even if data is loaded from a static JSON file - once it's parsed and stored as a JavaScript object in memory, it behaves like any other object—meaning it's mutable by reference.

This means that modifying a property of an object loaded from a JSON file will mutate the original object in memory, affecting all references to that object across the app.

To avoid accidental mutations, it's best to create a copy of the object (using methods like { ...obj } for shallow copies) before modifying it. This ensures that the original data remains unchanged and helps prevent unexpected side effects throughout the codebase.

Example of creating a copy to avoid mutation:

const content = { ...emails['Signup success'] };

This protects the original emails object from being modified, keeping the rest of the app safe from unintended changes.

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It's a small but important detail when dealing with mutable JavaScript objects loaded from static sources!

#passByReference #js #json #objects