ECMAScript® 2027 Language Specification

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Introduction
1 Scope
+2 Conformance
1. 2.1 Example Normative Optional Clause Heading
2. 2.2 Example Legacy Clause Heading
3. 2.3 Example Legacy Normative Optional Clause Heading
3 Normative References
+4 Overview
1. 4.1 Web Scripting
2. 4.2 Hosts and Implementations
3. +4.3 ECMAScript Overview
  1. 4.3.1 Objects
  2. 4.3.2 The Strict Variant of ECMAScript
4. +4.4 Terms and Definitions
5. 4.5 Organization of This Specification
+5 Notational Conventions
1. +5.1 Syntactic and Lexical Grammars
2. +5.2 Algorithm Conventions
+6 ECMAScript Data Types and Values
1. +6.1 ECMAScript Language Types
2. +6.2 ECMAScript Specification Types
+7 Abstract Operations
1. +7.1 Type Conversion
2. +7.2 Testing and Comparison Operations
3. +7.3 Operations on Objects
4. +7.4 Operations on Iterator Objects
5. +7.5 Operations on Disposable Objects
+8 Syntax-Directed Operations
1. 8.1 RS: Evaluation
2. +8.2 Scope Analysis
3. +8.3 Labels
4. +8.4 Function Name Inference
5. +8.5 Contains
  1. 8.5.1 SS: Contains
  2. 8.5.2 SS: ComputedPropertyContains
6. +8.6 Miscellaneous
+9 Executable Code and Execution Contexts
1. +9.1 Environment Records
  1. +9.1.1 The Environment Record Type Hierarchy
  2. +9.1.2 Environment Record Operations
2. +9.2 PrivateEnvironment Records
  1. +9.2.1 PrivateEnvironment Record Operations
    1. 9.2.1.1 NewPrivateEnvironment ( outerPrivateEnv )
    2. 9.2.1.2 ResolvePrivateIdentifier ( privateEnv, identifier )
3. +9.3 Realms
4. +9.4 Execution Contexts
5. +9.5 Jobs and Host Operations to Enqueue Jobs
6. +9.6 Agents
7. 9.7 Agent Clusters
8. 9.8 Forward Progress
9. +9.9 Processing Model of WeakRef and FinalizationRegistry Targets
10. 9.10 ClearKeptObjects ( )
11. 9.11 AddToKeptObjects ( value )
12. 9.12 CleanupFinalizationRegistry ( finalizationRegistry )
13. 9.13 CanBeHeldWeakly ( arg )
+10 Ordinary and Exotic Objects Behaviours
1. +10.1 Ordinary Object Internal Methods and Internal Slots
2. +10.2 ECMAScript Function Objects
3. +10.3 Built-in Function Objects
4. +10.4 Built-in Exotic Object Internal Methods and Slots
5. +10.5 Proxy Object Internal Methods and Internal Slots
+11 ECMAScript Language: Source Text
1. +11.1 Source Text
2. +11.2 Types of Source Code
+12 ECMAScript Language: Lexical Grammar
1. 12.1 Unicode Format-Control Characters
2. 12.2 White Space
3. 12.3 Line Terminators
4. 12.4 Comments
5. 12.5 Hashbang Comments
6. 12.6 Tokens
7. +12.7 Names and Keywords
  1. +12.7.1 Identifier Names
  2. 12.7.2 Keywords and Reserved Words
8. 12.8 Punctuators
9. +12.9 Literals
10. +12.10 Automatic Semicolon Insertion
+13 ECMAScript Language: Expressions
1. +13.1 Identifiers
2. +13.2 Primary Expression
3. +13.3 Left-Hand-Side Expressions
4. +13.4 Update Expressions
5. +13.5 Unary Operators
6. +13.6 Exponentiation Operator
  1. 13.6.1 RS: Evaluation
7. +13.7 Multiplicative Operators
  1. 13.7.1 RS: Evaluation
8. +13.8 Additive Operators
  1. +13.8.1 The Addition Operator ( + )
    1. 13.8.1.1 RS: Evaluation
  2. +13.8.2 The Subtraction Operator ( - )
    1. 13.8.2.1 RS: Evaluation
9. +13.9 Bitwise Shift Operators
10. +13.10 Relational Operators
  1. 13.10.1 RS: Evaluation
  2. 13.10.2 InstanceofOperator ( value, target )
11. +13.11 Equality Operators
  1. 13.11.1 RS: Evaluation
12. +13.12 Binary Bitwise Operators
  1. 13.12.1 RS: Evaluation
13. +13.13 Binary Logical Operators
  1. 13.13.1 RS: Evaluation
14. +13.14 Conditional Operator ( ? : )
  1. 13.14.1 RS: Evaluation
15. +13.15 Assignment Operators
16. +13.16 Comma Operator ( , )
  1. 13.16.1 RS: Evaluation
+14 ECMAScript Language: Statements and Declarations
1. +14.1 Statement Semantics
  1. 14.1.1 RS: Evaluation
2. +14.2 Block
3. +14.3 Declarations and the Variable Statement
4. +14.4 Empty Statement
  1. 14.4.1 RS: Evaluation
5. +14.5 Expression Statement
  1. 14.5.1 RS: Evaluation
6. +14.6 The if Statement
  1. 14.6.1 SS: Early Errors
  2. 14.6.2 RS: Evaluation
7. +14.7 Iteration Statements
8. +14.8 The continue Statement
  1. 14.8.1 SS: Early Errors
  2. 14.8.2 RS: Evaluation
9. +14.9 The break Statement
  1. 14.9.1 SS: Early Errors
  2. 14.9.2 RS: Evaluation
10. +14.10 The return Statement
  1. 14.10.1 RS: Evaluation
11. +14.11 The with Statement
  1. 14.11.1 SS: Early Errors
  2. 14.11.2 RS: Evaluation
12. +14.12 The switch Statement
13. +14.13 Labelled Statements
14. +14.14 The throw Statement
  1. 14.14.1 RS: Evaluation
15. +14.15 The try Statement
16. +14.16 The debugger Statement
  1. 14.16.1 RS: Evaluation
+15 ECMAScript Language: Functions and Classes
1. +15.1 Parameter Lists
2. +15.2 Function Definitions
3. +15.3 Arrow Function Definitions
4. +15.4 Method Definitions
5. +15.5 Generator Function Definitions
6. +15.6 Async Generator Function Definitions
7. +15.7 Class Definitions
8. +15.8 Async Function Definitions
9. +15.9 Async Arrow Function Definitions
10. +15.10 Tail Position Calls
+16 ECMAScript Language: Scripts and Modules
1. +16.1 Scripts
2. +16.2 Modules
+17 Error Handling and Language Extensions
1. 17.1 Forbidden Extensions
18 ECMAScript Standard Built-in Objects
+19 The Global Object
1. +19.1 Value Properties of the Global Object
2. +19.2 Function Properties of the Global Object
3. +19.3 Constructor Properties of the Global Object
4. +19.4 Other Properties of the Global Object
+20 Fundamental Objects
1. +20.1 Object Objects
  1. +20.1.1 The Object Constructor
    1. 20.1.1.1 Object ( value )
  2. +20.1.2 Properties of the Object Constructor