[Solved] What is wrong with this custom pipe implementation?import { PipeTransform, Injectable } from '@nestjs/common'; @Injectable() export class TrimPipe implements PipeTransform { transform(value:... | NestJS

NestJS - Pipes

What is wrong with this custom pipe implementation?

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

@Injectable()
export class TrimPipe implements PipeTransform {
  transform(value: any) {
    value.trim();
    return value;
  }
}

ANo @Injectable() decorator present

BThe trim() result is not returned, original value unchanged

CMissing ArgumentMetadata parameter in transform method

Dtransform method should not accept any parameters

Step-by-Step Solution

Solution:

Step 1: Understand string immutability in JavaScript
Strings are immutable, so value.trim() returns a new string but does not change original.
Step 2: Check return statement
The code returns original value without the trimmed result, so trimming has no effect.
Final Answer:
The trim() result is not returned, original value unchanged -> Option B
Quick Check:
Always return the result of string methods like trim() [OK]

Quick Trick: Return the result of string methods, don't ignore them [OK]

Common Mistakes:

Not returning trimmed string
Omitting parameters incorrectly
Missing @Injectable() decorator

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What is wrong with this custom pipe implementation?

Step 1: Understand string immutability in JavaScript

Step 2: Check return statement

Final Answer:

Quick Check:

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