TS2565 — Property Definitely Assigned But Never Read

このエラーの原因

You used the definite assignment assertion to tell TypeScript the property will be assigned, but the property is never actually read anywhere in the code.

修正方法

Remove the property if it is not needed. Use the property somewhere in the class. Remove the definite assignment assertion if the property is not being used.

class Foo {
  bar: string; // not assigned
}