NestJS ParseIntSlugPipe. Useful when you need to get slug or id from param.

parse-int-slug.pipe.ts

import {
  ArgumentMetadata,
  HttpStatus,
  Injectable,
  Optional,
  PipeTransform
} from '@nestjs/common';
import {
  ErrorHttpStatusCode,
  HttpErrorByCode
} from '@nestjs/common/utils/http-error-by-code.util';
import { isString } from 'class-validator';

export interface ParseIntSlugPipeOptions {
  errorHttpStatusCode?: ErrorHttpStatusCode;
  exceptionFactory?: (error: string) => any;
}

@Injectable()
export class ParseIntSlugPipe implements PipeTransform<string> {
  protected static slugRegExp = /^[A-Za-z0-9]+(?:-[A-Za-z0-9]+)*$/;
  protected exceptionFactory: (error: string) => any;

  constructor(@Optional() options?: ParseIntSlugPipeOptions) {
    options = options || {};
    const { exceptionFactory, errorHttpStatusCode = HttpStatus.BAD_REQUEST } =
      options;

    this.exceptionFactory =
      exceptionFactory ||
      (error => new HttpErrorByCode[errorHttpStatusCode](error));
  }

  async transform(
    value: string,
    metadata: ArgumentMetadata
  ): Promise<number | string> {
    if (this.isNumeric(value)) {
      return parseInt(value, 10);
    } else if (this.isSlug(value)) {
      return value;
    } else {
      throw this.exceptionFactory(
        'Validation failed (numeric string or slug string is expected)'
      );
    }
  }

  protected isNumeric(value: string): boolean {
    return (
      ['string', 'number'].includes(typeof value) &&
      /^-?\d+$/.test(value) &&
      isFinite(value as any)
    );
  }

  protected isSlug(str: unknown) {
    if (!isString(str)) {
      throw this.exceptionFactory('The value passed as Slug is not a string');
    }
    const pattern = ParseIntSlugPipe.slugRegExp;
    return pattern?.test(str);
  }
}