JavaScript Unicode-aware Strings Quiz

Question 1 of 16

What does JavaScript String `length` count?

Identify which text boundary or String operation the question is asking about.

Answer options A Grapheme clusters B 16-bit code units C Words D UTF-8 bytes

ECMAScript defines String length as the number of 16-bit elements.

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Question 2 of 16

What does `codePointAt(0)` do for a valid surrogate pair?

Identify which text boundary or String operation the question is asking about.

Answer options A Returns only the first surrogate B Combines the pair into one code point value C Converts the string to UTF-8 D Returns a grapheme cluster

A valid leading/trailing surrogate pair is interpreted as one Unicode code point.

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Question 3 of 16

Which operation is code-point-aware for String iteration?

Identify which text boundary or String operation the question is asking about.

Answer options A `text[0]` B `text.length` C `for...of` D `charCodeAt()`

The String iterator advances by code point.

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Question 4 of 16

Which constructor creates a string from code point values?

Identify which text boundary or String operation the question is asking about.

Answer options A String.fromCharCode B String.fromCodePoint C String.parse D String.codePoint

`String.fromCodePoint()` is designed for code point values.

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Question 5 of 16

Why is `[...text].length` not a visible-character counter?

Identify which text boundary or String operation the question is asking about.

Answer options A It counts bytes B It counts code points, not grapheme clusters C It counts words D It ignores ASCII

A grapheme cluster can contain multiple code points.

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Question 6 of 16

What does `isWellFormed()` report?

Identify which text boundary or String operation the question is asking about.

Answer options A Whether the text is NFC-normalized B Whether UTF-16 has no unpaired surrogates C Whether text is lowercase D Whether text is ASCII

It checks for unpaired surrogates.

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Question 7 of 16

What does `toWellFormed()` do?

Identify which text boundary or String operation the question is asking about.

Answer options A Deletes all non-ASCII text B Replaces unpaired surrogates with U+FFFD C Normalizes to NFC D Throws on malformed text

It returns a well-formed string with replacement characters for unpaired surrogates.

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Question 8 of 16

When should `normalize()` be used?

Identify which text boundary or String operation the question is asking about.

Answer options A Whenever text is compared B When a deliberate Unicode normalization policy is required C Only for ASCII D To count characters

Normalization is explicit; ordinary String operations do not implicitly normalize.

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Question 9 of 16

What can happen when slicing an emoji at a code-unit boundary?

Identify which text boundary or String operation the question is asking about.

Answer options A Nothing ever B A surrogate pair can be split C The emoji becomes two graphemes automatically D The string becomes UTF-8

String indices are code-unit positions, so a slice can land between pair members.

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Question 10 of 16

Which escape directly expresses U+1F600 as a code-point escape?

Identify which text boundary or String operation the question is asking about.

Answer options A \uD83D B \uDE00 C \u{1F600} D \x1F600

The braced Unicode escape accepts a code point value.

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Question 11 of 16

Which case-conversion claim is safest?

Identify which text boundary or String operation the question is asking about.

Answer options A Length always stays the same B Case conversion can change the resulting string C Case conversion is byte-based D Case conversion always normalizes

Unicode case conversion can change the sequence and length.

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Question 12 of 16

What coordinate system does `indexOf()` return?

Identify which text boundary or String operation the question is asking about.

Answer options A Grapheme indices B Code-unit indices C UTF-8 byte offsets D Word numbers

String positions use code-unit indices.

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Question 13 of 16

For a visible-text count, what concept matters?

Identify which text boundary or String operation the question is asking about.

Answer options A Code units B Code points only C Grapheme segmentation D Property enumeration

User-perceived text elements are a segmentation problem.

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Question 14 of 16

Which is an ECMAScript String fact?

Identify which text boundary or String operation the question is asking about.

Answer options A Strings are arrays of graphemes B String length counts 16-bit elements C Strings are UTF-8 byte arrays D All strings are normalized

ECMAScript String values are sequences of 16-bit elements.

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Question 15 of 16

Why can a supplementary code point use two code units?

Identify which text boundary or String operation the question is asking about.

Answer options A It is stored as UTF-8 B It is represented by a UTF-16 surrogate pair C It is always two graphemes D It uses two bytes only

Supplementary code points are represented by a leading/trailing surrogate pair in UTF-16.

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Question 16 of 16

Which iteration pattern avoids manual surrogate-pair handling?

Identify which text boundary or String operation the question is asking about.

Answer options A `for (let i=0; i<text.length; i++)` B `for (const ch of text)` C `text.split("")` D `text[0]`

The String iterator used by `for...of` is code-point-aware.

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JavaScript Unicode-aware Strings Quiz