answers.md

Sprint 1 — Mandatory Errors (Explanations)

0.js

• Error shown:
• Why it happens:
• MDN link (optional):
• Error shown: SyntaxError: Unexpected identifier 'is' on line 1.
• Why it happens: The file begins with plain English text that is not inside a comment or a quoted string. Node tries to interpret it as JavaScript code, but This is ... is not valid JS syntax, so parsing fails.
• MDN link (optional): https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Errors/Unexpected_token

1.js

• Error shown:
• Why it happens:
• MDN link (optional):
• Error shown: TypeError: Assignment to constant variable. on line 4.
• Why it happens: The variable age was declared with const, which prevents reassignment. The statement age = age + 1 attempts to update the value, causing the error.
• MDN link (optional): https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/const

2.js

• Error shown:
• Why it happens:
• MDN link (optional):
• Error shown: ReferenceError: Cannot access 'cityOfBirth' before initialization.
• Why it happens: The variable cityOfBirth is declared later in the file using let or const, but it is used before that declaration. JavaScript does not allow access to let/const variables before initialization (temporal dead zone).
• MDN link: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Errors/Cant_access_lexical_declaration_before_init

3.js

• Error shown:
• Why it happens:
• MDN link (optional):

3.js

• Error shown: TypeError: cardNumber.slice is not a function
• Why it happens: The variable cardNumber is a number, and numbers do not have the slice() method. The slice() method is only available on strings and arrays.
• Concept: Methods depend on data types in JavaScript.
• MDN link: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/slice

4.js

• Error shown:
• Why it happens:
• MDN link (optional):

4.js

• Error shown: SyntaxError: Invalid or unexpected token
• Why it happens: The variable name 12HourClockTime starts with a number. JavaScript identifiers cannot begin with a digit, so the parser throws a syntax error.
• Concept: Variable naming rules (identifiers must start with a letter, _, or $)
• MDN link: https://developer.mozilla.org/en-US/docs/Glossary/Identifier