[Solved] Given this custom pipe code, what will be the output if the input value is "42"?import { PipeTransform, Injectable, ArgumentMetadata, BadRequestException } from '@nestjs/common';... | NestJS

NestJS - Pipes

Given this custom pipe code, what will be the output if the input value is "42"?

import { PipeTransform, Injectable, ArgumentMetadata, BadRequestException } from '@nestjs/common';

@Injectable()
export class ParseIntPipe implements PipeTransform {
  transform(value: any, metadata: ArgumentMetadata) {
    const val = parseInt(value, 10);
    if (isNaN(val)) {
      throw new BadRequestException('Validation failed');
    }
    return val;
  }
}

AThrows BadRequestException

BReturns NaN

CReturns string "42"

DReturns number 42

Step-by-Step Solution

Solution:

Step 1: Analyze transform method logic
The pipe tries to convert the input string "42" to an integer using parseInt.
Step 2: Check for NaN and return value
Since "42" is a valid number string, parseInt returns 42, no exception is thrown, and 42 is returned.
Final Answer:
Returns number 42 -> Option D
Quick Check:
Valid number string input = returns number [OK]

Quick Trick: parseInt converts valid strings to numbers, else throws error [OK]

Common Mistakes:

Assuming string is returned
Expecting exception for valid number string
Confusing NaN with number 42

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Given this custom pipe code, what will be the output if the input value is "42"?

Step 1: Analyze transform method logic

Step 2: Check for NaN and return value

Final Answer:

Quick Check:

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