[Solved] Identify the mistake in this FileValidationPipe snippet:transform(file) { const allowedExtensions = ['jpg', 'png']; const extension = file.originalname.split('.').pop; if (!allowedExtensions.... | NestJS

NestJS - Pipes

Identify the mistake in this FileValidationPipe snippet:

transform(file) {
  const allowedExtensions = ['jpg', 'png'];
  const extension = file.originalname.split('.').pop;
  if (!allowedExtensions.includes(extension)) {
    throw new BadRequestException('Unsupported file type');
  }
  return file;
}

AThe allowedExtensions array should include uppercase extensions.

BThe <code>pop</code> method is not called as a function.

CThe pipe should check <code>file.mimetype</code> instead of extension.

DThe pipe should return null instead of the file.

Step-by-Step Solution

Solution:

Step 1: Analyze the extension extraction
The code uses file.originalname.split('.').pop but pop is a method and must be called as pop().
Step 2: Effect of missing parentheses
Without parentheses, extension is assigned the function reference, not the string extension.
Step 3: Correct usage
Change to file.originalname.split('.').pop() to get the file extension string.
Final Answer:
The pop method is not called as a function. -> Option B
Quick Check:
Remember to call array methods with parentheses [OK]

Quick Trick: Call pop() with parentheses to get last array element [OK]

Common Mistakes:

Forgetting parentheses on pop()
Ignoring case sensitivity in extensions
Checking mimetype instead of extension (not always wrong but different approach)

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More NestJS Quizzes

Identify the mistake in this FileValidationPipe snippet:

Step 1: Analyze the extension extraction

Step 2: Effect of missing parentheses

Step 3: Correct usage

Final Answer:

Quick Check:

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