Built-ins

Built-in	What's there	Not there, or different
Math	Every function and constant.
Number	isInteger, isSafeInteger, isFinite, isNaN, parseInt, parseFloat, the constants; toString(radix), toFixed, toPrecision, toExponential.
BigInt	BigInt(value) of a number, string, boolean or bigint; BigInt.asIntN, BigInt.asUintN; toString(radix), valueOf.	No toLocaleString.
Globals	parseInt, parseFloat, isNaN, isFinite, String(), Number(), Boolean().
String	The instance methods, String.fromCharCode, String.fromCodePoint. Case mapping uses Unicode's full rules; localeCompare uses the platform's collator.	No Intl.
Array	The instance methods, including find, findIndex, flatMap, at; Array.from, Array.of, Array.isArray, new Array(n).	Not the ES2023 methods: toSorted, toReversed, findLast, findLastIndex. Writing past the end throws a RangeError.
Map, Set	The whole API; new Map(entries), new Set(iterable).
Object	keys, values, entries, fromEntries.	On records; keys also on object types.
JSON	JSON.stringify of any value; JSON.parse(text) as T.	No replacer, indent or reviver. parse checks the text against T.
RegExp	Every feature and flag (dgimsuvy); exec, test, match, matchAll, search, replace, replaceAll, split.	A replacer with capture parameters needs a literal pattern.
Date	Constructors, Date.now, Date.parse, Date.UTC, the getters and setters, toISOString, toString and the other string forms.	No toLocale… methods. toString has Hermes's format.
Uint8Array	length, byteLength, subarray, slice, fill, indexOf, includes, set, forEach, map, reduce, join.	reduce needs an initial value.
Promise	Promise.all, Promise.resolve, Promise.reject, new Promise.	No race, allSettled, any or .then.
console	log, info, debug, warn, error: to the unified log on iOS, logcat on Android (tag Lucent).	Arguments print as String(value); a bigint with its n, as in JavaScript.
AbortController, AbortSignal	signal, abort(error?); aborted, throwIfAborted(), addEventListener("abort", …).	No signal.reason.

Not available: Intl, Symbol, WeakMap, WeakRef, Proxy, eval, TextEncoder and TextDecoder. Each is a compile error; for text, use utf8Encode and utf8Decode from lucent:core.