Draft ECMA-262 / August 02, 2019
+Draft ECMA-262 / August 04, 2019
ECMAScript® 2020 Language Specification
5.1.1Context-Free Grammars
5.1.2The Lexical and RegExp Grammars
A lexical grammar for ECMAScript is given in clause
Input elements other than white space and comments form the terminal symbols for the syntactic grammar for ECMAScript and are called ECMAScript tokens. These tokens are the reserved words, identifiers, literals, and punctuators of the ECMAScript language. Moreover, line terminators, although not considered to be tokens, also become part of the stream of input elements and guide the process of automatic semicolon insertion (/*…*/ regardless of whether it spans more than one line) is likewise simply discarded if it contains no line terminator; but if a
Input elements other than white space and comments form the terminal symbols for the syntactic grammar for ECMAScript and are called ECMAScript tokens. These tokens are the reserved words, identifiers, literals, and punctuators of the ECMAScript language. Moreover, line terminators, although not considered to be tokens, also become part of the stream of input elements and guide the process of automatic semicolon insertion (/*…*/ that spans more than one line) is replaced by a single line terminator, which becomes part of the stream of input elements for the syntactic grammar.
A RegExp grammar for ECMAScript is given in
Productions of the lexical and RegExp grammars are distinguished by having two colons “::” as separating punctuation. The lexical and RegExp grammars share some productions.
Syntax
11.3Line Terminators
Like white space code points, line terminator code points are used to improve source text readability and to separate tokens (indivisible lexical units) from each other. However, unlike white space code points, line terminators have some influence over the behaviour of the syntactic grammar. In general, line terminators may occur between any two tokens, but there are a few places where they are forbidden by the syntactic grammar. Line terminators also affect the process of automatic semicolon insertion (
A line terminator can occur within a
A line terminator must occur within a
Line terminators are included in the set of white space code points that are matched by the \s class in regular expressions.
The ECMAScript line terminator code points are listed in
Syntax
11.4Comments
Comments can be either single or multi-line. Multi-line comments cannot nest.
Because a single-line comment can contain any Unicode code point except a // marker to the end of the line. However, the
Comments behave like white space and are discarded except that, if a
Comments behave like white space and are discarded except that a
Syntax
Syntax
11.4.1Static Semantics: Early Errors
+-
+
- It is a Syntax Error if a
Module contains the source code matching this production.
+
A.1Lexical Grammar
A.1Lexical Grammar
B.1.2String Literals
B.1.3HTML-like Comments
-The syntax and semantics of
Syntax
-Similar to a
The HTML-like comment syntax used to be normative optional outside
Context-Free Grammars
The Lexical and RegExp Grammars
A lexical grammar for ECMAScript is given in clause
Input elements other than white space and comments form the terminal symbols for the syntactic grammar for ECMAScript and are called ECMAScript tokens. These tokens are the reserved words, identifiers, literals, and punctuators of the ECMAScript language. Moreover, line terminators, although not considered to be tokens, also become part of the stream of input elements and guide the process of automatic semicolon insertion (
Input elements other than white space and comments form the terminal symbols for the syntactic grammar for ECMAScript and are called ECMAScript tokens. These tokens are the reserved words, identifiers, literals, and punctuators of the ECMAScript language. Moreover, line terminators, although not considered to be tokens, also become part of the stream of input elements and guide the process of automatic semicolon insertion (
A RegExp grammar for ECMAScript is given in
Productions of the lexical and RegExp grammars are distinguished by having two colons “::” as separating punctuation. The lexical and RegExp grammars share some productions.
Syntax
Line Terminators
Like white space code points, line terminator code points are used to improve source text readability and to separate tokens (indivisible lexical units) from each other. However, unlike white space code points, line terminators have some influence over the behaviour of the syntactic grammar. In general, line terminators may occur between any two tokens, but there are a few places where they are forbidden by the syntactic grammar. Line terminators also affect the process of automatic semicolon insertion (
A line terminator can occur within a |MultiLineComment| but cannot occur within a |SingleLineComment|.
+A line terminator must occur within a |MultiLineComment| but cannot occur within a |SingleLineDelimitedComment| or a |SingleLineComment|.
Line terminators are included in the set of white space code points that are matched by the `\\s` class in regular expressions.
The ECMAScript line terminator code points are listed in
Syntax
Comments
Comments can be either single or multi-line. Multi-line comments cannot nest.
Because a single-line comment can contain any Unicode code point except a |LineTerminator| code point, and because of the general rule that a token is always as long as possible, a single-line comment always consists of all code points from the `//` marker to the end of the line. However, the |LineTerminator| at the end of the line is not considered to be part of the single-line comment; it is recognized separately by the lexical grammar and becomes part of the stream of input elements for the syntactic grammar. This point is very important, because it implies that the presence or absence of single-line comments does not affect the process of automatic semicolon insertion (see
Comments behave like white space and are discarded except that, if a |MultiLineComment| contains a line terminator code point, then the entire comment is considered to be a |LineTerminator| for purposes of parsing by the syntactic grammar.
+Comments behave like white space and are discarded except that a |MultiLineComment| or a |SingleLineHTMLCloseComment| is considered to be a |LineTerminator| for purposes of parsing by the syntactic grammar.
Syntax
Syntax
SingleLineComment :: `//` SingleLineCommentChars? + SingleLineHTMLOpenComment :: + `<!--` SingleLineCommentChars? + + SingleLineHTMLCloseComment :: + LineTerminatorSequence HTMLCloseComment + + HTMLCloseComment :: + WhiteSpaceSequence? SingleLineDelimitedCommentSequence? `-->` SingleLineCommentChars? + + SingleLineDelimitedCommentSequence :: + SingleLineDelimitedComment WhiteSpaceSequence? SingleLineDelimitedCommentSequence? + + WhiteSpaceSequence :: + WhiteSpace WhiteSpaceSequence? + SingleLineCommentChars :: SingleLineCommentChar SingleLineCommentChars? SingleLineCommentChar :: SourceCharacter but not LineTerminator + + SingleLineDelimitedComment :: + `/*` SingleLineDelimitedCommentChars? `*/` + + SingleLineDelimitedCommentChars :: + SingleLineNotAsteriskChar SingleLineDelimitedCommentChars? + `*` SingleLinePostAsteriskCommentChars? + + SingleLineNotAsteriskChar :: + SourceCharacter but not one of `*` or LineTerminator + + SingleLinePostAsteriskCommentChars :: + SingleLineNotForwardSlashOrAsteriskChar SingleLineDelimitedCommentChars? + `*` SingleLinePostAsteriskCommentChars? + + SingleLineNotForwardSlashOrAsteriskChar :: + SourceCharacter but not one of `/` or `*` or LineTerminatorStatic Semantics: Early Errors
+-
+
- It is a Syntax Error if a |Module| contains the source code matching this production. +
Lexical Grammar
String Literals
HTML-like Comments
-The syntax and semantics of
Syntax
-Similar to a |MultiLineComment| that contains a line terminator code point, a |SingleLineHTMLCloseComment| is considered to be a |LineTerminator| for purposes of parsing by the syntactic grammar.
+The HTML-like comment syntax used to be normative optional outside |Module|s.