ISO/IEC Information technology Programming languages, their environments and system software interfaces ECMAScript language specification

Transcription

1 INTERNATIONAL STANDARD ISO/IEC Third edition Information technology Programming languages, their environments and system software interfaces ECMAScript language specification Technologies de l'information Langages de programmation, leurs environnements et interfaces de logiciel système Spécification du langage ECMAscript Reference number ISO/IEC 2011

2 COPYRIGHT PROTECTED DOCUMENT ISO/IEC 2011 All rights reserved. Unless otherwise specif ied, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocop ying and microfilm, w ithout permission in wr iting from either ISO at the address be low or ISO's member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel Fax copyright@iso.org Web Published in Switzerland ii ISO/IEC 2011 All rights reserved

3 Contents Page Foreword...viii Introduction...ix 1 Scope Conformance Normative references Overview Web Scripting Language Overview Objects The Strict Variant of ECMAScript Terms and definitions Notational Conventions Syntactic and Lexical Grammars Context-Free Grammars The Lexical and RegExp Grammars The Numeric String Grammar The Syntactic Grammar The JSON Grammar Grammar Notation Algorithm Conventions Source Text Lexical Conventions Unicode Format-Control Characters White Space Line Terminators Comments Tokens Identifier Names and Identifiers Reserved Words Punctuators Literals Null Literals Boolean Literals Numeric Literals String Literals Regular Expression Literals Automatic Semicolon Insertion Rules of Automatic Semicolon Insertion Examples of Automatic Semicolon Insertion Types The Undefined Type The Null Type The Boolean Type The String Type The Number Type The Object Type Property Attributes Object Internal Properties and Methods...31 ISO/IEC 2011 All rights reserved iii

4 8.7 The Reference Specification Type GetValue (V) PutValue (V, W) The List Specification Type The Completion Specification Type The Property Descriptor and Property Identifier Specification Types IsAccessorDescriptor ( Desc ) IsDataDescriptor ( Desc ) IsGenericDescriptor ( Desc ) FromPropertyDescriptor ( Desc ) ToPropertyDescriptor ( Obj ) The Lexical Environment and Environment Record Specification Types Algorithms for Object Internal Methods [[GetOwnProperty]] (P) [[GetProperty]] (P) [[Get]] (P) [[CanPut]] (P) [[Put]] ( P, V, Throw ) [[HasProperty]] (P) [[Delete]] (P, Throw) [[DefaultValue]] (hint) [[DefineOwnProperty]] (P, Desc, Throw) Type Conversion and Testing ToPrimitive ToBoolean ToNumber ToNumber Applied to the String Type ToInteger ToInt32: (Signed 32 Bit Integer) ToUint32: (Unsigned 32 Bit Integer) ToUint16: (Unsigned 16 Bit Integer) ToString ToString Applied to the Number Type ToObject CheckObjectCoercible IsCallable The SameValue Algorithm Executable Code and Execution Contexts Types of Executable Code Strict Mode Code Lexical Environments Environment Records Lexical Environment Operations The Global Environment Execution Contexts Identifier Resolution Establishing an Execution Context Entering Global Code Entering Eval Code Entering Function Code Declaration Binding Instantiation Arguments Object Expressions Primary Expressions The this Keyword Identifier Reference Literal Reference Array Initialiser...63 iv ISO/IEC 2011 All rights reserved

5 Object Initialiser The Grouping Operator Left-Hand-Side Expressions Property Accessors The new Operator Function Calls Argument Lists Function Expressions Postfix Expressions Postfix Increment Operator Postfix Decrement Operator Unary Operators The delete Operator The void Operator The typeof Operator Prefix Increment Operator Prefix Decrement Operator Unary + Operator Unary - Operator Bitwise NOT Operator ( ~ ) Logical NOT Operator (! ) Multiplicative Operators Applying the * Operator Applying the / Operator Applying the % Operator Additive Operators The Addition operator ( + ) The Subtraction Operator ( - ) Applying the Additive Operators to Numbers Bitwise Shift Operators The Left Shift Operator ( << ) The Signed Right Shift Operator ( >> ) The Unsigned Right Shift Operator ( >>> ) Relational Operators The Less-than Operator ( < ) The Greater-than Operator ( > ) The Less-than-or-equal Operator ( <= ) The Greater-than-or-equal Operator ( >= ) The Abstract Relational Comparison Algorithm The instanceof operator The in operator Equality Operators The Equals Operator ( == ) The Does-not-equals Operator (!= ) The Abstract Equality Comparison Algorithm The Strict Equals Operator ( === ) The Strict Does-not-equal Operator (!== ) The Strict Equality Comparison Algorithm Binary Bitwise Operators Binary Logical Operators Conditional Operator (? : ) Assignment Operators Simple Assignment ( = ) Compound Assignment ( op= ) Comma Operator (, ) Statements Block...86 ISO/IEC 2011 All rights reserved v

6 12.2 Variable Statement Strict Mode Restrictions Empty Statement Expression Statement The if Statement Iteration Statements The do-while Statement The while Statement The for Statement The for-in Statement The continue Statement The break Statement The return Statement The with Statement Strict Mode Restrictions The switch Statement Labelled Statements The throw Statement The try Statement Strict Mode Restrictions The debugger statement Function Definition Strict Mode Restrictions Creating Function Objects [[Call]] [[Construct]] The [[ThrowTypeError]] Function Object Program Directive Prologues and the Use Strict Directive Standard Built-in ECMAScript Objects The Global Object Value Properties of the Global Object Function Properties of the Global Object URI Handling Function Properties Constructor Properties of the Global Object Other Properties of the Global Object Object Objects The Object Constructor Called as a Function The Object Constructor Properties of the Object Constructor Properties of the Object Prototype Object Properties of Object Instances Function Objects The Function Constructor Called as a Function The Function Constructor Properties of the Function Constructor Properties of the Function Prototype Object Properties of Function Instances Array Objects The Array Constructor Called as a Function The Array Constructor Properties of the Array Constructor Properties of the Array Prototype Object Properties of Array Instances String Objects The String Constructor Called as a Function The String Constructor vi ISO/IEC 2011 All rights reserved

7 Properties of the String Constructor Properties of the String Prototype Object Properties of String Instances Boolean Objects The Boolean Constructor Called as a Function The Boolean Constructor Properties of the Boolean Constructor Properties of the Boolean Prototype Object Properties of Boolean Instances Number Objects The Number Constructor Called as a Function The Number Constructor Properties of the Number Constructor Properties of the Number Prototype Object Properties of Number Instances The Math Object Value Properties of the Math Object Function Properties of the Math Object Date Objects Overview of Date Objects and Definitions of Abstract Operators The Date Constructor Called as a Function The Date Constructor Properties of the Date Constructor Properties of the Date Prototype Object Properties of Date Instances RegExp (Regular Expression) Objects Patterns Pattern Semantics The RegExp Constructor Called as a Function The RegExp Constructor Properties of the RegExp Constructor Properties of the RegExp Prototype Object Properties of RegExp Instances Error Objects The Error Constructor Called as a Function The Error Constructor Properties of the Error Constructor Properties of the Error Prototype Object Properties of Error Instances Native Error Types Used in This Standard NativeError Object Structure The JSON Object The JSON Grammar parse ( text [, reviver ] ) stringify ( value [, replacer [, space ] ] ) Errors Annex A (informative) Grammar Summary Annex B (informative) Compatibility Annex C (informative) The Strict Mode of ECMAScript Annex D (informative) Corrections and Clarifications in the 3 rd Edition with Possible 2 nd Edition Compatibility Impact Annex E (informative) Additions and Changes in the 3 rd Edition that Introduce Incompatibilities with the 2 nd Edition Bibliography ISO/IEC 2011 All rights reserved vii

8 Foreword ISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commission) form the specialized system for worldwide standardization. National bodies that are members of ISO or IEC participate in the development of International Standards through technical committees established by the respective organization to deal with particular fields of tec hnical activity. ISO an d IEC technical committees collaborate in fields of mutual interest. Other international organizations, governmental and non-governmental, in liaison with ISO a nd IEC, also take part in the work. In the field of information technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of the joint tech nical committee is to prepare International Standards. Draft International Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as an International Standard requires approval by at least 75 % of the national bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights. ISO/IEC was prepared by Ecma International (as ECMA-262) and was adopted, under a special fasttrack procedure, by Joint Technical Committee ISO/IEC JTC 1, Information technology, in parallel with its approval by national bodies of ISO and IEC. This third edition cancels and replaces the second edition (ISO/IEC 16262:2002), which has been technically revised. viii ISO/IEC 2011 All rights reserved

9 Introduction This International Standard is based on several originating technologies, the most well-known being JavaScript (Netscape) and JScript (Microsoft). The lang uage was invented by Bren dan Eich at Netscape and first a ppeared in that company s Navigator 2.0 browser. It has appeared in all subsequent browsers from Netscape and in all browsers from Microsoft starting with Internet Explorer 3.0. The development of this Internation al Standard sta rted in Nove mber The first editi on of this International Standard was adopted by the Ecma General Assembly of June That International Standard was submitted to IS O/IEC JTC 1 for ad option under the fast-track procedure, and approved as ISO/IEC 16262, first edition, in April The second edition of this International Standard introduced powerful regular expressions, better string handling, new control statements, try/catch exception handling, tighter definition of errors, formattin g for numeric output and minor changes in anticipation of forthcoming internationalization facilities and future language growth. The second edition of the ECMAScript standard was published as ISO/IEC in June Since publication of the second edition of ISO/IE C 16262:2002, ECMAScript has achieved massive adoption in conjunction with the World Wide Web where it ha s become the programming language that is supported by essentially all web browsers. Significant work was done to develop a third edition of ECMAScript. Although that wo rk was not completed and not publi shed as a n ew edition of ECMAScript, it informs continuin g evolution of the language. The present third edition of ISO/IEC (published as ECMA-262 5th edition) codifies de facto interpretations of the l anguage specification that have become common among browser implementations and adds support for new features that have emerged since the publication of the third edition. Such features include accessor properties, reflective cre ation and i nspection of objects, program control of prop erty attributes, additional array manipulati on functions, support for the JSON o bject encoding format, and a strict mode that provides enhanced error checking and program security. ECMAScript is a vibrant l anguage and the evolutio n of the lan guage is n ot complete. Significant technical enhancement will continue with future editions of this International Standard. ISO/IEC 2011 All rights reserved ix

10 INTERNATIONAL STANDARD Information technology Programming languages, their environments and system software interfaces ECMAScript language specification 1 Scope This International Standard defines the ECMAScript scripting language. 2 Conformance A conforming implementation of ECMAScript must provide and support all the types, values, objects, properties, functions, and program syntax and semantics described in this International Standard. A conforming implementation of this International Standard shall interpret characters in conformance with the Unicode Standard, Version 3.0 or later, and ISO/IEC with either UCS-2 or UTF-16 as the adopted encoding form, implementation level 3. If the adopted ISO/IEC subset is not otherwise specified, it is presumed to be the BMP subset, collection 300. If the adopted encoding form is not otherwise specified, it presumed to be the UTF-16 encoding form. A conforming implementation of ECMAScript is permitted to provide additional types, values, objects, properties, and functions beyond those described in this International Standard. In particular, a conforming implementation of ECMAScript is permitted to provide properties not described in this International Standard, and values for those properties, for objects that are described in this International Standard. A conforming implementation of ECMAScript is permitted to support program and regular expression syntax not described in this International Standard. In particular, a conforming implementation of ECMAScript is permitted to support program syntax that makes use of the future reserved words listed in of this International Standard. 3 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO/IEC 10646, ISO/IEC 2011 All rights reserved 1