nest/packages/common/pipes/default-value.pipe.ts

import { Injectable } from '../decorators/core/injectable.decorator';
import {
  ArgumentMetadata,
  PipeTransform,
} from '../interfaces/features/pipe-transform.interface';
import { isNil, isNumber } from '../utils/shared.utils';

/**
 * Defines the built-in DefaultValue Pipe
 *
 * @see [Built-in Pipes](https://docs.nestjs.com/pipes#built-in-pipes)
 *
 * @publicApi
 */
@Injectable()
export class DefaultValuePipe<T = any, R = any>
  implements PipeTransform<T, T | R>
{
  constructor(protected readonly defaultValue: R) {}

  transform(value?: T, _metadata?: ArgumentMetadata): T | R {
    if (
      isNil(value) ||
      (isNumber(value) && isNaN(value as unknown as number))
    ) {
      return this.defaultValue;
    }
    return value;
  }
}