RenaiApp/src/main/entities/library/tag.ts

import { Entity, ManyToMany } from 'typeorm';
import { MultiNamed } from './bases/multi-named';
import { Book } from './book';

@Entity()
export class Tag extends MultiNamed {
  @ManyToMany(() => Book, {
    nullable: false,
    onDelete: 'CASCADE',
    onUpdate: 'CASCADE',
  })
  public books: Promise<Book[]>;
}