[Solved] What happens if the custom pipe below receives the input "abc"?export class ParseIntPipe implements PipeTransform { transform(value: any) { const val = parseInt(value, 10);... | NestJS

NestJS - Pipes

What happens if the custom pipe below receives the input "abc"?

export class ParseIntPipe implements PipeTransform {
  transform(value: any) {
    const val = parseInt(value, 10);
    if (isNaN(val)) {
      throw new Error('Invalid number');
    }
    return val;
  }
}

AReturns NaN

BReturns 0

CReturns string "abc"

DThrows an Error with message 'Invalid number'

Step-by-Step Solution

Solution:

Step 1: Check parseInt result for input "abc"
parseInt("abc", 10) returns NaN because "abc" is not a number.
Step 2: Evaluate error throwing condition
Since val is NaN, the pipe throws an Error with message 'Invalid number'.
Final Answer:
Throws an Error with message 'Invalid number' -> Option D
Quick Check:
Invalid number input = throws Error [OK]

Quick Trick: Invalid number strings cause error throw in custom pipe [OK]

Common Mistakes:

Expecting NaN return
Assuming string is returned
Thinking 0 is returned

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What happens if the custom pipe below receives the input "abc"?

Step 1: Check parseInt result for input "abc"

Step 2: Evaluate error throwing condition

Final Answer:

Quick Check:

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