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abstract

Marks a class or member that cannot be instantiated or must be implemented.

Since TS 2.0 Spec ↗

Syntax

abstract class Name { abstract member(): Type }

Examples

abstract class Shape {
  abstract area(): number;
  describe() {
    return `area is ${this.area()}`;
  }
}

class Square extends Shape {
  constructor(private s: number) { super(); }
  area() { return this.s * this.s; }
}

// new Shape(); // Error: cannot create instance of abstract class

Notes

An abstract class cannot be instantiated directly and may declare abstract members with no implementation. Subclasses must implement every abstract member. TypeScript also supports abstract construct signatures via `abstract new (...) => T`.

See also