[Solved] Given this custom pipe code, what will be the output if the input value is "123"?import { PipeTransform, Injectable, BadRequestException } from '@nestjs/common';... | NestJS

NestJS - Pipes

Given this custom pipe code, what will be the output if the input value is "123"?

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

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

Input: "123"

AReturns NaN

BThrows BadRequestException

CReturns string "123"

DReturns number 123

Step-by-Step Solution

Solution:

Step 1: Understand parseInt behavior on string "123"
parseInt("123", 10) converts the string "123" to the number 123.
Step 2: Check the validation condition
Since 123 is a valid number, isNaN(val) is false, so no exception is thrown and the number 123 is returned.
Final Answer:
Returns number 123 -> Option D
Quick Check:
parseInt("123") = 123 [OK]

Quick Trick: parseInt("123") returns number 123, no error [OK]

Common Mistakes:

Thinking it returns string instead of number
Assuming it throws error for numeric strings
Confusing NaN with valid number

Master "Pipes" in NestJS

9 interactive learning modes - each teaches the same concept differently

Learn Why Deep Visual Try Challenge Project Recall Perf

More NestJS Quizzes

Given this custom pipe code, what will be the output if the input value is "123"?

Step 1: Understand parseInt behavior on string "123"

Step 2: Check the validation condition

Final Answer:

Quick Check:

Want More Practice?