EC
TS2704
TypeScriptERRORNotableTypeHIGH confidence

The operand of a 'delete' operator cannot be a read-only property.

Production Risk

Build will fail; resolve before shipping.

What this means

A type-checking error (TS2704): The operand of a 'delete' operator cannot be a read-only property.. This diagnostic is emitted by the TypeScript compiler when the operand of a 'delete' operator cannot be a read-only property..

Why it happens
  1. 1Attempting to modify a property or variable declared as readonly
How to reproduce

TypeScript compiler reports TS2704 during type checking.

trigger — this will error
trigger — this will error
// Triggers TS2704
// The operand of a 'delete' operator cannot be a read-only property.

expected output

error TS2704: The operand of a 'delete' operator cannot be a read-only property.

Fix

Remove the readonly modifier or create a mutable copy

WHEN When you need to mutate a readonly property

Remove the readonly modifier or create a mutable copy
// Create a mutable copy
const mutable = { ...readonlyObject };
mutable.property = newValue;
// Or remove readonly from the type definition
type MyType = { property: string }; // not readonly

Why this works

readonly properties enforce immutability at the type level; create a copy to modify.

Sources
Official documentation ↗

TypeScript Compiler Diagnostics

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