Input Validation with Regex Quiz: Test Your High School Web Dev Skills

📚 Quick Study Guide: Input Validation with Regex

• 🛡️ What is Input Validation? It's the process of ensuring that user input meets specific criteria before it's processed or stored. Essential for security (preventing injections, malformed data) and data integrity.
• 🔍 What is Regex (Regular Expressions)? A sequence of characters that defines a search pattern. Used for pattern matching, searching, and manipulating strings.
• 🔑 Common Regex Metacharacters:
  • ⚫ `.` - Matches any single character (except newline).
  • ⭐ `*` - Matches zero or more occurrences of the preceding character.
  • ➕ `+` - Matches one or more occurrences of the preceding character.
  • ❓ `?` - Matches zero or one occurrence of the preceding character.
  • ⬆️ `^` - Matches the beginning of the string.
  • ⬇️ `$` - Matches the end of the string.
  • 📦 `[]` - Matches any one of the characters inside the brackets (e.g., `[0-9]` for digits).
  • 🚫 `[^]` - Matches any character NOT inside the brackets.
  • 🔗 `()` - Groups characters together and creates a capturing group.
  • ↔️ `|` - Acts as an OR operator.
  • 🔙 `\` - Escapes a special character or denotes a special sequence (e.g., `\d` for digit, `\w` for word character, `\s` for whitespace).
• ✅ Why use Regex for Validation? It provides a powerful and concise way to define complex patterns for data like email addresses, phone numbers, passwords, dates, etc., ensuring data conforms to expected formats.
• ⚠️ Best Practices: Always validate both client-side (for user experience) and server-side (for security). Never trust client-side validation alone.

🧠 Practice Quiz: Regex Input Validation

1. What regex pattern would correctly validate a 5-digit ZIP code (e.g., 12345)?
A) `^\d{5}$`
B) `[0-9]{5}`
C) `\d*`
D) `^[0-9]+$`

2. Which regex pattern would match a valid email address structure (e.g., `[email protected]`)?
A) `.*@.*`
B) `^\w+@\w+\.\w+$`
C) `^[\w.-]+@[\w.-]+\.[a-zA-Z]{2,6}$`
D) `[a-zA-Z0-9]+@[a-zA-Z0-9]+\.[a-zA-Z]{2,}`

3. To validate a username that must be alphanumeric (letters and numbers only) and between 3 and 16 characters long, which regex is most appropriate?
A) `^[a-zA-Z0-9]{3,16}$`
B) `\w{3,16}`
C) `[a-zA-Z0-9]*`
D) `^\D{3,16}$`

4. Which metacharacter matches the beginning of a string in regex?
A) `$`
B) `*`
C) `^`
D) `.`

5. A password requires at least one uppercase letter, one lowercase letter, one digit, and be a minimum of 8 characters long. Which regex concept is typically used to enforce such multiple conditions within a single pattern?
A) Alternation (`|`)
B) Character Classes (`[]`)
C) Lookaheads (`(?=...)`)
D) Quantifiers (`{n,m}`)

6. What does the regex pattern `\d+` match?
A) Any single digit.
B) Zero or more digits.
C) One or more digits.
D) Exactly one digit.

7. To validate a phone number in the format `XXX-XXX-XXXX` (where X is a digit), which regex pattern would work?
A) `\d{3}-\d{3}-\d{4}`
B) `[0-9]{3}-[0-9]{3}-[0-9]{4}`
C) `^\d{3}-\d{3}-\d{4}$`
D) `\d{10}`

✅ Answer Key