TypeScript
Cannot assign to read only property
Cannot assign to '{0}' because it is a read-only property.TypeScript rejected an assignment because the target property is marked readonly.
Error AtlasError Documentation and ResolutionObserved message
Cannot assign to '{0}' because it is a read-only property.Why it happens
- Code attempts to modify a property declared with readonly.
- A library type exposes an immutable object shape.
- A function mutates input values that were intentionally typed as readonly.
How to fix it
- Stop mutating the readonly property directly.
- Create a new object with the updated value instead of changing the existing one.
- Review the type definition and remove readonly only if mutation is genuinely intended.
Official reference
TypeScript Handbook: Object TypesRelated errors
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