Register Typeorm Data Listeners without using decorators

typeormDataListeners.ts

import { EventListenerType } from 'typeorm/metadata/types/EventListenerTypes';
import { getManager, EntitySchema } from 'typeorm';
import { EntityListenerMetadata } from 'typeorm/metadata/EntityListenerMetadata';

export function addDatabaseListener (entity: EntitySchema<any> | Function | string, type: EventListenerType, handler: Function) {
  const meta = getManager().connection.getMetadata(entity);
  let r = '_' +  Math.random().toString(36).substring(7);
  (meta.target as any).prototype[r] = handler;
  const el = new EntityListenerMetadata({
    entityMetadata: meta,
    args: {
      target: meta.target as any,
      propertyName: r,
      type: type
    }
  })
  if (type === 'after-insert') {
    meta.afterInsertListeners.push(el);
  } else if (type === 'before-insert') {
    meta.beforeInsertListeners.push(el);
  } else if (type === 'after-update') {
    meta.afterUpdateListeners.push(el);
  } else if (type === 'before-update') {
    meta.beforeUpdateListeners.push(el);
  } else if (type === 'before-remove') {
    meta.beforeRemoveListeners.push(el);
  } else if (type === 'after-remove') {
    meta.afterRemoveListeners.push(el);
  } else if (type === 'after-load') {
    meta.afterLoadListeners.push(el);
  }
  meta.ownListeners.push(el);
  meta.listeners.push(el);
}


export function removeDatabaseListener (entity: EntitySchema<any> | Function | string,type: EventListenerType, handler: Function) {
  const meta = getManager().connection.getMetadata(entity);
  let listeners = [];
  if (type === 'after-insert') {
    listeners = meta.beforeInsertListeners;
  } else if (type === 'before-insert') {
    listeners = meta.afterInsertListeners;
  } else if (type === 'after-update') {
    listeners = meta.afterUpdateListeners;
  } else if (type === 'before-update') {
    listeners = meta.beforeUpdateListeners;
  } else if (type === 'before-remove') {
    listeners = meta.beforeRemoveListeners;
  } else if (type === 'after-remove') {
    listeners = meta.afterRemoveListeners;
  } else if (type === 'after-load') {
    listeners = meta.afterLoadListeners;
  }

  const protoHandler = Object.entries((entity as any).prototype).find(e => e[1] === handler);
  if (!protoHandler) {
    return;
  }
  const index = listeners.findIndex(e => e.propertyName === protoHandler[0]);
  if (index !== -1) {
    listeners.splice(index, 1);
    delete (entity as any).prototype[protoHandler[0]];
  }
}