class validation in nestjs with string property which validate number

Question

nestJS class-validator: property is string: check the value is between 100 to 5000

i need to validate dto property that validate string number between 100 and 5000

Answer 1

You can use the following custom validator:

@ValidatorConstraint({ name: 'customText', async: false })
export class CustomTextLength implements ValidatorConstraintInterface {
  validate(text: string, args: ValidationArguments) {
    const asNum = Number(text);
    if ( Number.isNaN(asNum) ) return false; 
    return asNum > 100 && asNum < 5000;
  }

  defaultMessage(args: ValidationArguments) {
    return 'string number ($value) is too big or too small';
  }
}

Nevertheless you should probably just use a transform pipe and then validate the actual result of this transformation to a number.