PR #6

This document is a preview of merging PR #6 as commit 15fbf0d5d686b10d5467a8e85a91e67f20df4960.

Do not reference it as authoritative in any way. Instead, see the living specification at https://github.com/tc39/proposal-bigint-from-exponential.

Multipage preference

Proposal proposal-bigint-from-exponential

Stage 1 Draft / September 12, 2026

Bigint from exponential

7 Abstract Operations

7.1 Type Conversion

7.1.4 ToNumber ( arg )

The abstract operation ToNumber takes argument arg (an ECMAScript language value) and returns either a normal completion containing a Number or a throw completion. It converts arg to a value of type Number.

7.1.4.1 ToNumber Applied to the String Type

The abstract operation StringToNumber specifies how to convert a String value to a Number value, using the following grammar.

Syntax

StringNumericLiteral ::: StrWhiteSpaceopt StrWhiteSpaceopt StrNumericLiteral StrWhiteSpaceopt StrWhiteSpace ::: StrWhiteSpaceChar StrWhiteSpaceopt StrWhiteSpaceChar ::: WhiteSpace LineTerminator StrNumericLiteral ::: StrDecimalLiteral NonDecimalIntegerLiteral[~Sep] StrDecimalLiteral ::: StrUnsignedDecimalLiteral + StrUnsignedDecimalLiteral - StrUnsignedDecimalLiteral StrUnsignedDecimalLiteral ::: Infinity DecimalDigits[~Sep] . DecimalDigits[~Sep]opt ExponentPart[~Sep]opt . DecimalDigits[~Sep] ExponentPart[~Sep]opt DecimalDigits[~Sep] ExponentPart[~Sep]opt

All grammar symbols not explicitly defined above have the definitions used in the Lexical Grammar for numeric literals (12.9.3)

Note

Some differences should be noted between the syntax of a StringNumericLiteral and a NumericLiteral:

7.1.4.1.1 StringToNumber ( string )

The abstract operation StringToNumber takes argument string (a String) and returns a Number. It performs the following steps when called:

  1. Let literal be ParseText(string, StringNumericLiteral).
  2. If literal is a List of errors, return NaN.
  3. Return the StringNumericValue of literal.

7.1.4.1.2 Runtime Semantics: MV

7.1.16 StringToBigInt ( string )

The abstract operation StringToBigInt takes argument string (a String) and returns a BigInt or undefined. It performs the following steps when called:

  1. Let literal be ParseText(string, StringIntegerLiteralStringNumericLiteral).
  2. If literal is a List of errors, return undefined.
  3. Let mv be the MV of literal.
  4. Assert: mv is an integer.
  5. If mv is not an integer, return undefined.
  6. Return ℤ(mv).

7.1.16.1 StringIntegerLiteral Grammar

StringToBigInt uses the following grammar.

Syntax

StringIntegerLiteral ::: StrWhiteSpaceopt StrWhiteSpaceopt StrIntegerLiteral StrWhiteSpaceopt StrIntegerLiteral ::: SignedInteger[~Sep] NonDecimalIntegerLiteral[~Sep]

7.1.16.2 Runtime Semantics: MV

12 ECMAScript Language: Lexical Grammar

12.9 Literals

12.9.3 Numeric Literals

Syntax

NumericLiteralSeparator :: _ XXXNumericLiteral :: DecimalLiteral[~Legacy] DecimalBigIntegerLiteral NonDecimalIntegerLiteral[+Sep] NonDecimalIntegerLiteral[+Sep] BigIntLiteralSuffix LegacyOctalIntegerLiteral NumericLiteral :: DecimalLiteral[+Legacy] DecimalBigIntegerLiteral NonDecimalIntegerLiteral[+Sep] NonDecimalIntegerLiteral[+Sep] BigIntLiteralSuffix LegacyOctalIntegerLiteral XXXDecimalBigIntegerLiteral :: 0 BigIntLiteralSuffix NonZeroDigit DecimalDigits[+Sep]opt BigIntLiteralSuffix NonZeroDigit NumericLiteralSeparator DecimalDigits[+Sep] BigIntLiteralSuffix DecimalBigIntegerLiteral :: DecimalLiteral[~Legacy] BigIntLiteralSuffix NonDecimalIntegerLiteral[Sep] :: BinaryIntegerLiteral[?Sep] OctalIntegerLiteral[?Sep] HexIntegerLiteral[?Sep] BigIntLiteralSuffix :: n XXXDecimalLiteral :: DecimalIntegerLiteral[~Legacy] . DecimalDigits[+Sep]opt ExponentPart[+Sep]opt . DecimalDigits[+Sep] ExponentPart[+Sep]opt DecimalIntegerLiteral[~Legacy] ExponentPart[+Sep]opt DecimalLiteral[Legacy] :: DecimalIntegerLiteral[?Legacy] . DecimalDigits[+Sep]opt ExponentPart[+Sep]opt . DecimalDigits[+Sep] ExponentPart[+Sep]opt DecimalIntegerLiteral[?Legacy] ExponentPart[+Sep]opt XXXDecimalIntegerLiteral :: 0 NonZeroDigit NonZeroDigit NumericLiteralSeparatoropt DecimalDigits[+Sep] NonOctalDecimalIntegerLiteral DecimalIntegerLiteral[Legacy] :: 0 NonZeroDigit NonZeroDigit NumericLiteralSeparatoropt DecimalDigits[+Sep] [+Legacy] NonOctalDecimalIntegerLiteral DecimalDigits[Sep] :: DecimalDigit DecimalDigits[?Sep] DecimalDigit [+Sep] DecimalDigits[+Sep] NumericLiteralSeparator DecimalDigit DecimalDigit :: one of 0 1 2 3 4 5 6 7 8 9 NonZeroDigit :: one of 1 2 3 4 5 6 7 8 9 ExponentPart[Sep] :: ExponentIndicator SignedInteger[?Sep] ExponentIndicator :: one of e E SignedInteger[Sep] :: DecimalDigits[?Sep] + DecimalDigits[?Sep] - DecimalDigits[?Sep] BinaryIntegerLiteral[Sep] :: 0b BinaryDigits[?Sep] 0B BinaryDigits[?Sep] BinaryDigits[Sep] :: BinaryDigit BinaryDigits[?Sep] BinaryDigit [+Sep] BinaryDigits[+Sep] NumericLiteralSeparator BinaryDigit BinaryDigit :: one of 0 1 OctalIntegerLiteral[Sep] :: 0o OctalDigits[?Sep] 0O OctalDigits[?Sep] OctalDigits[Sep] :: OctalDigit OctalDigits[?Sep] OctalDigit [+Sep] OctalDigits[+Sep] NumericLiteralSeparator OctalDigit LegacyOctalIntegerLiteral :: 0 OctalDigit LegacyOctalIntegerLiteral OctalDigit NonOctalDecimalIntegerLiteral :: 0 NonOctalDigit LegacyOctalLikeDecimalIntegerLiteral NonOctalDigit NonOctalDecimalIntegerLiteral DecimalDigit LegacyOctalLikeDecimalIntegerLiteral :: 0 OctalDigit LegacyOctalLikeDecimalIntegerLiteral OctalDigit OctalDigit :: one of 0 1 2 3 4 5 6 7 NonOctalDigit :: one of 8 9 HexIntegerLiteral[Sep] :: 0x HexDigits[?Sep] 0X HexDigits[?Sep] HexDigits[Sep] :: HexDigit HexDigits[?Sep] HexDigit [+Sep] HexDigits[+Sep] NumericLiteralSeparator HexDigit HexDigit :: one of 0 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F

The SourceCharacter immediately following a NumericLiteral must not be an IdentifierStart or DecimalDigit.

Note

For example: 3in is an error and not the two input elements 3 and in.

12.9.3.1 Static Semantics: Early Errors

DecimalBigIntegerLiteral :: DecimalLiteral[~Legacy] BigIntLiteralSuffix NumericLiteral :: LegacyOctalIntegerLiteral DecimalIntegerLiteral :: NonOctalDecimalIntegerLiteral
  • It is a Syntax Error if IsStrict(this production) is true.
Note
In non-strict code, this syntax is Legacy.

12.9.3.3 Static Semantics: NumericValue

The syntax-directed operation NumericValue takes no arguments and returns a Number or a BigInt. It is defined piecewise over the following productions:

NumericLiteral :: DecimalLiteral
  1. Return RoundMVResult(MV of DecimalLiteral).
 NumericLiteral :: NonDecimalIntegerLiteral
  1. Return 𝔽(MV of NonDecimalIntegerLiteral).
 NumericLiteral :: LegacyOctalIntegerLiteral
  1. Return 𝔽(MV of LegacyOctalIntegerLiteral).
 NumericLiteral :: NonDecimalIntegerLiteral BigIntLiteralSuffix
  1. Return the BigInt value for the MV of NonDecimalIntegerLiteral.
 DecimalBigIntegerLiteral :: DecimalLiteral[~Legacy] BigIntLiteralSuffix
  1. Let mv be the MV of DecimalLiteral.
  2. Assert: mv is an integer.
  3. Return ℤ(mv).
 XXXDecimalBigIntegerLiteral :: 0 BigIntLiteralSuffix
  1. Return 0ℤ.
 XXXDecimalBigIntegerLiteral :: NonZeroDigit BigIntLiteralSuffix
  1. Return the BigInt value for the MV of NonZeroDigit.
 XXXDecimalBigIntegerLiteral :: NonZeroDigit DecimalDigits BigIntLiteralSuffix NonZeroDigit NumericLiteralSeparator DecimalDigits BigIntLiteralSuffix
  1. Let n be the number of code points in DecimalDigits, excluding all occurrences of NumericLiteralSeparator.
  2. Let mv be (the MV of NonZeroDigit × 10n) plus the MV of DecimalDigits.
  3. Return ℤ(mv).

Annex A (informative) Grammar Summary

A.6 Number Conversions

StringNumericLiteral ::: StrWhiteSpaceopt StrWhiteSpaceopt StrNumericLiteral StrWhiteSpaceopt StrWhiteSpace ::: StrWhiteSpaceChar StrWhiteSpaceopt StrWhiteSpaceChar ::: WhiteSpace LineTerminator StrNumericLiteral ::: StrDecimalLiteral NonDecimalIntegerLiteral[~Sep] StrDecimalLiteral ::: StrUnsignedDecimalLiteral + StrUnsignedDecimalLiteral - StrUnsignedDecimalLiteral StrUnsignedDecimalLiteral ::: Infinity DecimalDigits[~Sep] . DecimalDigits[~Sep]opt ExponentPart[~Sep]opt . DecimalDigits[~Sep] ExponentPart[~Sep]opt DecimalDigits[~Sep] ExponentPart[~Sep]opt

All grammar symbols not explicitly defined by the StringNumericLiteral grammar have the definitions used in the Lexical Grammar for numeric literals.

StringIntegerLiteral ::: StrWhiteSpaceopt StrWhiteSpaceopt StrIntegerLiteral StrWhiteSpaceopt StrIntegerLiteral ::: SignedInteger[~Sep] NonDecimalIntegerLiteral[~Sep]

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