12.8 Literals
12.8.1 Null Literals
Syntax
12.8.2 Boolean Literals
Syntax
12.8.3 Numeric Literals
Syntax
The
For example: 3in is an error and not the two input elements 3 and in.
A conforming implementation, when processing
12.8.3.1 Static Semantics: MV
A numeric literal stands for a value of the Number type or the BigInt type.
-
The MV of
NumericLiteral :: DecimalLiteral DecimalLiteral . -
The MV of
NonDecimalIntegerLiteral :: BinaryIntegerLiteral BinaryIntegerLiteral . -
The MV of
NonDecimalIntegerLiteral :: OctalIntegerLiteral OctalIntegerLiteral . -
The MV of
NonDecimalIntegerLiteral :: HexIntegerLiteral HexIntegerLiteral . -
The MV of
DecimalLiteral :: DecimalIntegerLiteral . DecimalIntegerLiteral . -
The MV of
DecimalLiteral :: DecimalIntegerLiteral . DecimalDigits DecimalIntegerLiteral plus (the MV ofDecimalDigits × 10-n), where n is the number of code points inDecimalDigits , excluding all occurrences ofNumericLiteralSeparator . -
The MV of
DecimalLiteral :: DecimalIntegerLiteral . ExponentPart DecimalIntegerLiteral × 10e, where e is the MV ofExponentPart . -
The MV of
DecimalLiteral :: DecimalIntegerLiteral . DecimalDigits ExponentPart DecimalIntegerLiteral plus (the MV ofDecimalDigits × 10-n)) × 10e, where n is the number of code points inDecimalDigits , excluding all occurrences ofNumericLiteralSeparator and e is the MV ofExponentPart . -
The MV of
DecimalLiteral :: . DecimalDigits DecimalDigits × 10-n, where n is the number of code points inDecimalDigits , excluding all occurrences ofNumericLiteralSeparator . -
The MV of
DecimalLiteral :: . DecimalDigits ExponentPart DecimalDigits × 10e - n, where n is the number of code points inDecimalDigits , excluding all occurrences ofNumericLiteralSeparator , and e is the MV ofExponentPart . -
The MV of
DecimalLiteral :: DecimalIntegerLiteral DecimalIntegerLiteral . -
The MV of
DecimalLiteral :: DecimalIntegerLiteral ExponentPart DecimalIntegerLiteral × 10e, where e is the MV ofExponentPart . -
The MV of
DecimalIntegerLiteral :: 0 -
The MV of
DecimalIntegerLiteral :: NonZeroDigit NonZeroDigit . -
The MV of
DecimalIntegerLiteral :: NonZeroDigit NumericLiteralSeparator opt DecimalDigits NonZeroDigit × 10n) plus the MV ofDecimalDigits , where n is the number of code points inDecimalDigits , excluding all occurrences ofNumericLiteralSeparator . -
The MV of
DecimalDigits :: DecimalDigit DecimalDigit . -
The MV of
DecimalDigits :: DecimalDigits DecimalDigit DecimalDigits × 10) plus the MV ofDecimalDigit . -
The MV of
DecimalDigits :: DecimalDigits NumericLiteralSeparator DecimalDigit DecimalDigits × 10) plus the MV ofDecimalDigit . -
The MV of
ExponentPart :: ExponentIndicator SignedInteger SignedInteger . -
The MV of
SignedInteger :: DecimalDigits DecimalDigits . -
The MV of
SignedInteger :: + DecimalDigits DecimalDigits . -
The MV of
SignedInteger :: - DecimalDigits DecimalDigits . -
The MV of
DecimalDigit :: 0 HexDigit :: 0 OctalDigit :: 0 BinaryDigit :: 0 -
The MV of
DecimalDigit :: 1 NonZeroDigit :: 1 HexDigit :: 1 OctalDigit :: 1 BinaryDigit :: 1 -
The MV of
DecimalDigit :: 2 NonZeroDigit :: 2 HexDigit :: 2 OctalDigit :: 2 -
The MV of
DecimalDigit :: 3 NonZeroDigit :: 3 HexDigit :: 3 OctalDigit :: 3 -
The MV of
DecimalDigit :: 4 NonZeroDigit :: 4 HexDigit :: 4 OctalDigit :: 4 -
The MV of
DecimalDigit :: 5 NonZeroDigit :: 5 HexDigit :: 5 OctalDigit :: 5 -
The MV of
DecimalDigit :: 6 NonZeroDigit :: 6 HexDigit :: 6 OctalDigit :: 6 -
The MV of
DecimalDigit :: 7 NonZeroDigit :: 7 HexDigit :: 7 OctalDigit :: 7 -
The MV of
DecimalDigit :: 8 NonZeroDigit :: 8 HexDigit :: 8 -
The MV of
DecimalDigit :: 9 NonZeroDigit :: 9 HexDigit :: 9 -
The MV of
HexDigit :: a HexDigit :: A -
The MV of
HexDigit :: b HexDigit :: B -
The MV of
HexDigit :: c HexDigit :: C -
The MV of
HexDigit :: d HexDigit :: D -
The MV of
HexDigit :: e HexDigit :: E -
The MV of
HexDigit :: f HexDigit :: F -
The MV of
BinaryIntegerLiteral :: 0b BinaryDigits BinaryDigits . -
The MV of
BinaryIntegerLiteral :: 0B BinaryDigits BinaryDigits . -
The MV of
BinaryDigits :: BinaryDigit BinaryDigit . -
The MV of
BinaryDigits :: BinaryDigits BinaryDigit BinaryDigits × 2) plus the MV ofBinaryDigit . -
The MV of
BinaryDigits :: BinaryDigits NumericLiteralSeparator BinaryDigit BinaryDigits × 2) plus the MV ofBinaryDigit . -
The MV of
OctalIntegerLiteral :: 0o OctalDigits OctalDigits . -
The MV of
OctalIntegerLiteral :: 0O OctalDigits OctalDigits . -
The MV of
OctalDigits :: OctalDigit OctalDigit . -
The MV of
OctalDigits :: OctalDigits OctalDigit OctalDigits × 8) plus the MV ofOctalDigit . -
The MV of
OctalDigits :: OctalDigits NumericLiteralSeparator OctalDigit OctalDigits × 8) plus the MV ofOctalDigit . -
The MV of
HexIntegerLiteral :: 0x HexDigits HexDigits . -
The MV of
HexIntegerLiteral :: 0X HexDigits HexDigits . -
The MV of
HexDigits :: HexDigit HexDigit . -
The MV of
HexDigits :: HexDigits HexDigit HexDigits × 16) plus the MV ofHexDigit . -
The MV of
HexDigits :: HexDigits NumericLiteralSeparator HexDigit HexDigits × 16) plus the MV ofHexDigit .
12.8.3.2 Static Semantics: NumericValue
- Return the
Number value that results from rounding the MV ofDecimalLiteral as described below.
- Return the
Number value that results from rounding the MV ofNonDecimalIntegerLiteral as described below.
Once the exact MV for a numeric literal has been determined, it is then rounded to a value of the Number type. If the MV is 0, then the rounded value is 0 digit or the 0 digit and then incrementing the literal at the 20th significant digit position. A digit is significant if it is not part of an
-
it is not
0; or -
there is a non-zero digit to its left and there is a non-zero digit, not in the
ExponentPart , to its right.
- Return the BigInt value that represents the MV of
NonDecimalIntegerLiteral .
- Return
0 ℤ.
- Return the BigInt value that represents the MV of
NonZeroDigit .
- Let n be the number of code points in
DecimalDigits , excluding all occurrences ofNumericLiteralSeparator . - Let mv be (the MV of
NonZeroDigit × 10) plus the MV ofDecimalDigits . - Return
ℤ (mv).
12.8.4 String Literals
A string literal is 0 or more Unicode code points enclosed in single or double quotes. Unicode code points may also be represented by an escape sequence. All code points may appear literally in a string literal except for the closing quote code points, U+005C (REVERSE SOLIDUS), U+000D (CARRIAGE RETURN), and U+000A (LINE FEED). Any code points may appear in the form of an escape sequence. String literals evaluate to ECMAScript String values. When generating these String values Unicode code points are UTF-16 encoded as defined in
Syntax
A conforming implementation, when processing
The definition of the nonterminal
<LF> and <CR> cannot appear in a string literal, except as part of a \n or \u000A.
12.8.4.1 Static Semantics: SV
A string literal stands for a value of the String type. The String value (SV) of the literal is described in terms of String values contributed by the various parts of the string literal. As part of this process, some Unicode code points within the string literal are interpreted as having a
-
The SV of
StringLiteral :: " " -
The SV of
StringLiteral :: ' ' -
The SV of
DoubleStringCharacters :: DoubleStringCharacter DoubleStringCharacters string-concatenation of the SV ofDoubleStringCharacter and the SV ofDoubleStringCharacters . -
The SV of
SingleStringCharacters :: SingleStringCharacter SingleStringCharacters string-concatenation of the SV ofSingleStringCharacter and the SV ofSingleStringCharacters . -
The SV of
DoubleStringCharacter :: SourceCharacter but not one of " or\ orLineTerminator UTF16EncodeCodePoint on the code point value ofSourceCharacter . -
The SV of
DoubleStringCharacter :: <LS> -
The SV of
DoubleStringCharacter :: <PS> -
The SV of
DoubleStringCharacter :: LineContinuation -
The SV of
SingleStringCharacter :: SourceCharacter but not one of ' or\ orLineTerminator UTF16EncodeCodePoint on the code point value ofSourceCharacter . -
The SV of
SingleStringCharacter :: <LS> -
The SV of
SingleStringCharacter :: <PS> -
The SV of
SingleStringCharacter :: LineContinuation -
The SV of
EscapeSequence :: 0 -
The SV of
CharacterEscapeSequence :: SingleEscapeCharacter SingleEscapeCharacter according toTable 36 .
| Escape Sequence | Code Unit Value | Unicode Character Name | Symbol |
|---|---|---|---|
\b
|
0x0008
|
BACKSPACE | <BS> |
\t
|
0x0009
|
CHARACTER TABULATION | <HT> |
\n
|
0x000A
|
LINE FEED (LF) | <LF> |
\v
|
0x000B
|
LINE TABULATION | <VT> |
\f
|
0x000C
|
FORM FEED (FF) | <FF> |
\r
|
0x000D
|
CARRIAGE RETURN (CR) | <CR> |
\"
|
0x0022
|
QUOTATION MARK |
"
|
\'
|
0x0027
|
APOSTROPHE |
'
|
\\
|
0x005C
|
REVERSE SOLIDUS |
\
|
-
The SV of
NonEscapeCharacter :: SourceCharacter but not one of EscapeCharacter orLineTerminator UTF16EncodeCodePoint on the code point value ofSourceCharacter . -
The SV of
HexEscapeSequence :: x HexDigit HexDigit HexEscapeSequence . -
The SV of
Hex4Digits :: HexDigit HexDigit HexDigit HexDigit Hex4Digits . -
The SV of
UnicodeEscapeSequence :: u{ CodePoint } UTF16EncodeCodePoint on the MV ofCodePoint .
12.8.4.2 Static Semantics: MV
-
The MV of
HexEscapeSequence :: x HexDigit HexDigit HexDigit ) plus the MV of the secondHexDigit . -
The MV of
Hex4Digits :: HexDigit HexDigit HexDigit HexDigit HexDigit ) plus (0x100 × the MV of the secondHexDigit ) plus (0x10 × the MV of the thirdHexDigit ) plus the MV of the fourthHexDigit .
12.8.5 Regular Expression Literals
A regular expression literal is an input element that is converted to a RegExp object (see === to each other even if the two literals' contents are identical. A RegExp object may also be created at runtime by new RegExp or calling the RegExp
The productions below describe the syntax for a regular expression literal and are used by the input element scanner to find the end of the regular expression literal. The source text comprising the
An implementation may extend the ECMAScript Regular Expression grammar defined in
Syntax
Regular expression literals may not be empty; instead of representing an empty regular expression literal, the code unit sequence // starts a single-line comment. To specify an empty regular expression, use: /(?:)/.
12.8.5.1 Static Semantics: Early Errors
-
It is a Syntax Error if
IdentifierPart contains a Unicode escape sequence.
12.8.5.2 Static Semantics: BodyText
- Return the source text that was recognized as
RegularExpressionBody .
12.8.5.3 Static Semantics: FlagText
- Return the source text that was recognized as
RegularExpressionFlags .
12.8.6 Template Literal Lexical Components
Syntax
A conforming implementation must not use the extended definition of
12.8.6.1 Static Semantics: TV and TRV
A template literal component is interpreted as a sequence of Unicode code points. The Template Value (TV) of a literal component is described in terms of String values (
-
The TV and TRV of
NoSubstitutionTemplate :: ` ` -
The TV and TRV of
TemplateHead :: ` ${ -
The TV and TRV of
TemplateMiddle :: } ${ -
The TV and TRV of
TemplateTail :: } ` -
The TV of
TemplateCharacters :: TemplateCharacter TemplateCharacters undefined if either the TV ofTemplateCharacter isundefined or the TV ofTemplateCharacters isundefined . Otherwise, it is thestring-concatenation of the TV ofTemplateCharacter and the TV ofTemplateCharacters . -
The TV of
TemplateCharacter :: SourceCharacter but not one of ` or\ or$ orLineTerminator UTF16EncodeCodePoint on the code point value ofSourceCharacter . -
The TV of
TemplateCharacter :: $ -
The TV of
TemplateCharacter :: \ EscapeSequence SV ofEscapeSequence . -
The TV of
TemplateCharacter :: \ NotEscapeSequence undefined . -
The TV of
TemplateCharacter :: LineTerminatorSequence LineTerminatorSequence . -
The TV of
LineContinuation :: \ LineTerminatorSequence -
The TRV of
TemplateCharacters :: TemplateCharacter TemplateCharacters string-concatenation of the TRV ofTemplateCharacter and the TRV ofTemplateCharacters . -
The TRV of
TemplateCharacter :: SourceCharacter but not one of ` or\ or$ orLineTerminator UTF16EncodeCodePoint on the code point value ofSourceCharacter . -
The TRV of
TemplateCharacter :: $ -
The TRV of
TemplateCharacter :: \ EscapeSequence string-concatenation of the code unit 0x005C (REVERSE SOLIDUS) and the TRV ofEscapeSequence . -
The TRV of
TemplateCharacter :: \ NotEscapeSequence string-concatenation of the code unit 0x005C (REVERSE SOLIDUS) and the TRV ofNotEscapeSequence . -
The TRV of
EscapeSequence :: 0 -
The TRV of
NotEscapeSequence :: 0 DecimalDigit string-concatenation of the code unit 0x0030 (DIGIT ZERO) and the TRV ofDecimalDigit . -
The TRV of
NotEscapeSequence :: x [lookahead ∉ HexDigit ] -
The TRV of
NotEscapeSequence :: x HexDigit [lookahead ∉ HexDigit ]string-concatenation of the code unit 0x0078 (LATIN SMALL LETTER X) and the TRV ofHexDigit . -
The TRV of
NotEscapeSequence :: u [lookahead ∉ HexDigit ][lookahead ≠ { ] -
The TRV of
NotEscapeSequence :: u HexDigit [lookahead ∉ HexDigit ]string-concatenation of the code unit 0x0075 (LATIN SMALL LETTER U) and the TRV ofHexDigit . -
The TRV of
NotEscapeSequence :: u HexDigit HexDigit [lookahead ∉ HexDigit ]string-concatenation of the code unit 0x0075 (LATIN SMALL LETTER U), the TRV of the firstHexDigit , and the TRV of the secondHexDigit . -
The TRV of
NotEscapeSequence :: u HexDigit HexDigit HexDigit [lookahead ∉ HexDigit ]string-concatenation of the code unit 0x0075 (LATIN SMALL LETTER U), the TRV of the firstHexDigit , the TRV of the secondHexDigit , and the TRV of the thirdHexDigit . -
The TRV of
NotEscapeSequence :: u { [lookahead ∉ HexDigit ]string-concatenation of the code unit 0x0075 (LATIN SMALL LETTER U) and the code unit 0x007B (LEFT CURLY BRACKET). -
The TRV of
NotEscapeSequence :: u { NotCodePoint [lookahead ∉ HexDigit ]string-concatenation of the code unit 0x0075 (LATIN SMALL LETTER U), the code unit 0x007B (LEFT CURLY BRACKET), and the TRV ofNotCodePoint . -
The TRV of
NotEscapeSequence :: u { CodePoint [lookahead ∉ HexDigit ][lookahead ≠ } ]string-concatenation of the code unit 0x0075 (LATIN SMALL LETTER U), the code unit 0x007B (LEFT CURLY BRACKET), and the TRV ofCodePoint . -
The TRV of
DecimalDigit :: one of 0 1 2 3 4 5 6 7 8 9 UTF16EncodeCodePoint on the single code point matched by this production. -
The TRV of
CharacterEscapeSequence :: NonEscapeCharacter SV ofNonEscapeCharacter . -
The TRV of
SingleEscapeCharacter :: one of ' " \ b f n r t v UTF16EncodeCodePoint on the single code point matched by this production. -
The TRV of
HexEscapeSequence :: x HexDigit HexDigit string-concatenation of the code unit 0x0078 (LATIN SMALL LETTER X), the TRV of the firstHexDigit , and the TRV of the secondHexDigit . -
The TRV of
UnicodeEscapeSequence :: u Hex4Digits string-concatenation of the code unit 0x0075 (LATIN SMALL LETTER U) and the TRV ofHex4Digits . -
The TRV of
UnicodeEscapeSequence :: u{ CodePoint } string-concatenation of the code unit 0x0075 (LATIN SMALL LETTER U), the code unit 0x007B (LEFT CURLY BRACKET), the TRV ofCodePoint , and the code unit 0x007D (RIGHT CURLY BRACKET). -
The TRV of
Hex4Digits :: HexDigit HexDigit HexDigit HexDigit string-concatenation of the TRV of the firstHexDigit , the TRV of the secondHexDigit , the TRV of the thirdHexDigit , and the TRV of the fourthHexDigit . -
The TRV of
HexDigits :: HexDigits HexDigit string-concatenation of the TRV ofHexDigits and the TRV ofHexDigit . -
The TRV of
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 UTF16EncodeCodePoint on the single code point matched by this production. -
The TRV of
LineContinuation :: \ LineTerminatorSequence string-concatenation of the code unit 0x005C (REVERSE SOLIDUS) and the TRV ofLineTerminatorSequence . -
The TRV of
LineTerminatorSequence :: <LF> -
The TRV of
LineTerminatorSequence :: <CR> -
The TRV of
LineTerminatorSequence :: <LS> -
The TRV of
LineTerminatorSequence :: <PS> -
The TRV of
LineTerminatorSequence :: <CR> <LF>
TV excludes the code units of