Modern ECMAScript Update Pass — Quiz

Check your understanding of recent standardized ECMAScript additions and their ownership in the curriculum.

Skip a hard question and review it before your results.

Questions and answer options can shuffle between attempts.

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Question 1 of 16

What is the purpose of Math.sumPrecise()?

Answer options A To sum an iterable while reducing precision loss B To convert Numbers to BigInts C To round every value to an integer D To sort numeric values

Math.sumPrecise is a 2026 addition for summing Numbers while minimizing precision loss.

Question 2 of 16

What does Iterator.concat() produce?

Answer options A An iterator that yields values from the supplied iterators in sequence B A Promise for an array C A single string D A Set with deduplication

Iterator.concat combines iterator sources into one iterator without requiring an intermediate array.

Question 3 of 16

What can Array.fromAsync() consume?

Answer options A Async iterables and other async sources B Only DOM nodes C Only strings D Only synchronous arrays

Array.fromAsync creates an Array from asynchronous input, including async iterables.

Question 4 of 16

What question does Error.isError() answer?

Answer options A Whether a value is an Error object B Whether an error message is empty C Whether a Promise rejected D Whether code is in strict mode

Error.isError is a 2026 static Error method for identifying Error objects.

Question 5 of 16

What does Uint8Array.prototype.toHex() return?

Answer options A A hexadecimal string representing the bytes B A Number containing the byte count C A new ArrayBuffer D A decoded Unicode string

The 2026 Uint8Array additions provide standardized byte-to-hex conversion.

Question 6 of 16

What does Uint8Array.fromHex() create?

Answer options A A Uint8Array from a hexadecimal string B A String object C A DataView with text methods D A BigInt

Uint8Array.fromHex converts pairs of hexadecimal digits into byte values.

Question 7 of 16

What is Uint8Array.prototype.toBase64() for?

Answer options A Encoding bytes as Base64 B Parsing JavaScript source C Creating a BigInt D Changing endianness

The standardized method encodes byte data as Base64 without requiring a browser-specific binary-string trick.

Question 8 of 16

What does Uint8Array.fromBase64() return?

Answer options A A Uint8Array containing decoded bytes B A decoded DOM element C A Promise D A regular expression

The method decodes Base64 text into a Uint8Array of bytes.

Question 9 of 16

What extra information can the modern JSON.parse reviver receive?

Answer options A The matched source text for the current value B The current DOM element C The network response headers D The original Promise

The 2026 reviver context can expose the original JSON source segment for the value.

Question 10 of 16

Why use JSON.rawJSON()?

Answer options A To mark valid JSON text for direct inclusion in JSON.stringify output B To parse arbitrary JavaScript source C To disable JSON escaping everywhere D To create a JSON module

JSON.rawJSON marks a primitive value for controlled raw inclusion in JSON.stringify output.

Question 11 of 16

What does Set.prototype.union() return?

Answer options A A Set containing values from both sets B An Array of duplicate pairs C A Map of indexes D A Promise

Set union is part of the modern Set methods standardized in ECMAScript 2025.

Question 12 of 16

What problem does RegExp.escape() solve?

Answer options A It escapes text so it can be safely inserted as literal RegExp pattern text B It executes a regular expression faster C It converts a RegExp into a URL D It disables Unicode matching

RegExp.escape produces pattern text that treats the supplied string as literal content.

Question 13 of 16

What do inline RegExp modifiers control?

Answer options A Selected flags for a nested part of a pattern B The JavaScript execution mode C The object prototype D The string encoding

Modern RegExp modifier syntax can enable or disable selected flags within a nested pattern region.

Question 14 of 16

What is Promise.try() designed to normalize?

Answer options A A function that may return a value or throw into a Promise result B A network request into a fetch response C A generator into a class D A callback into an event

Promise.try invokes a function and turns a returned value or thrown error into the corresponding Promise outcome.

Question 15 of 16

What does Float16Array add to the TypedArray family?

Answer options A A 16-bit binary floating-point element type B A 16-bit UTF-16 string type C A signed 16-byte integer type D A text encoding API

Float16Array stores IEEE 754 binary16 values; Math.f16round rounds a Number to that representation.

Question 16 of 16

What is the important property of toSorted()?

Answer options A It returns a sorted copy without mutating the original array B It sorts only strings C It mutates and freezes the original array D It returns a Promise

toSorted is part of the non-mutating array method family standardized in ECMAScript 2023.

Modern ECMAScript Update Pass — Quiz