EC
TS1267
TypeScriptERRORNotableSyntaxHIGH confidence

Property 'X' cannot have an initializer because it is marked abstract.

Production Risk

Build will fail; resolve before shipping.

What this means

A syntax error (TS1267): Property 'X' cannot have an initializer because it is marked abstract.. This diagnostic is emitted by the TypeScript compiler when property 'X' cannot have an initializer because it is marked abstract..

Why it happens
  1. 1A concrete class extends an abstract class but does not implement all abstract members
How to reproduce

TypeScript compiler reports TS1267 during type checking.

trigger — this will error
trigger — this will error
// Triggers TS1267
// Property 'X' cannot have an initializer because it is marked abstract.

expected output

error TS1267: Property 'X' cannot have an initializer because it is marked abstract.

Fix

Implement all abstract members

WHEN Extending an abstract class

Implement all abstract members
abstract class Base {
  abstract doWork(): void;
}
class Derived extends Base {
  doWork(): void { /* implementation */ }
}

Why this works

All abstract members must be implemented in concrete subclasses.

Sources
Official documentation ↗

TypeScript Compiler Diagnostics

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