TypeScript Language Specification v1.5

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DeclarationElement: ExportAssignment AmbientExternalModuleDeclaration export opt InterfaceDeclaration export opt TypeAliasDeclaration export opt ImportDeclaration export opt AmbientDeclaration export opt ExternalImportDeclaration When a TypeScript program is compiled, all of the program's source files are processed together. Statements and declarations in different source files can depend on each other, possibly in a circular fashion. By default, a JavaScript output file is generated for each implementation source file in a compilation, but no output is generated from declaration source files. The source elements permitted in a TypeScript implementation source file are a superset of those supported by JavaScript. Specifically, TypeScript extends the JavaScript grammar's existing VariableDeclaration (section 5.1) and FunctionDeclaration (section 6.1) productions, and adds TypeAliasDeclaration (section 3.9), InterfaceDeclaration (section 7.1), ClassDeclaration (section 8.1), EnumDeclaration (section 9.1), ModuleDeclaration (section 10.1), ImportDeclaration (section 10.3), ExternalImportDeclaration (section 11.2.2), ExportAssignment (section 11.2.4), AmbientDeclaration (section 12.1), and AmbientExternalModuleDeclaration (section 12.2) productions. Declaration source files are restricted to contain declarations only. Declaration source files can be used to declare the static type information associated with existing JavaScript code in an adjunct manner. They are entirely optional but enable the TypeScript compiler and tools to provide better verification and assistance when integrating existing JavaScript code and libraries in a TypeScript application. Implementation and declaration source files that contain no import or export declarations form the single global module. Entities declared in the global module are in scope everywhere in a program. Initialization order of the source files that make up the global module ultimately depends on the order in which the generated JavaScript files are loaded at run-time (which, for example, may be controlled by tags that reference the generated JavaScript files). Implementation and declaration source files that contain at least one external import declaration, export assignment, or top-level exported declaration are considered separate external modules. Entities declared in an external module are in scope only in that module, but exported entities can be imported into other modules using import declarations. Initialization order of external modules is determined by the module loader being and is not specified by the TypeScript language. However, it is generally the case that non-circularly dependent modules are automatically loaded and initialized in the correct order. External modules can additionally be declared using AmbientExternalModuleDeclarations in the global module that directly specify the external module names as string literals. This is described further in section 12.2. 144
11.1.1 Source Files Dependencies The TypeScript compiler automatically determines a source file's dependencies and includes those dependencies in the program being compiled. The determination is made from "reference comments" and external import declarations as follows: A comment of the form /// adds a dependency on the source file specified in the path argument. The path is resolved relative to the directory of the containing source file. An external import declaration that specifies a relative external module name (section 11.2.1) resolves the name relative to the directory of the containing source file. If a source file with the resulting path and file extension '.ts' exists, that file is added as a dependency. Otherwise, if a source file with the resulting path and file extension '.d.ts' exists, that file is added as a dependency. An external import declaration that specifies a top-level external module name (section 11.2.1) resolves the name in a host dependent manner (typically by resolving the name relative to a module name space root or searching for the name in a series of directories). If a source file with extension '.ts' or '.d.ts' corresponding to the reference is located, that file is added as a dependency. Any files included as dependencies in turn have their references analyzed in a transitive manner until all dependencies have been determined. 11.2 External Modules External modules are separately loaded bodies of code referenced using external module names. External modules can be likened to functions that are loaded and executed once to initialize their associated module instance. Entities declared in an external module are private and inaccessible elsewhere unless they are exported. External modules are written as separate source files that contain at least one external import declaration, export assignment, or top-level exported declaration. Specifically, if a source file contains at least one ExternalImportDeclaration, ExportAssignment, top-level exported VariableDeclaration, top-level exported FunctionDeclaration, top-level exported ClassDeclaration, top-level exported InterfaceDeclaration, top-level exported TypeAliasDeclaration, top-level exported EnumDeclaration, top-level exported ModuleDeclaration, top-level exported ImportDeclaration, or top-level exported AmbientDeclaration, 145
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TypeScript Language Specification V
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Table of Contents 1 Introduction ..
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4.9.1 Standard Function Expressions
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9.1 Enum Declarations .............
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1 Introduction JavaScript applicati
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1.1 Ambient Declarations An ambient
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call '$' as a function. The behavio
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function getX(p: Point) { return p.
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This TypeScript class declaration c
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Section 9 describes how programmers
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Interface definitions, like the one
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TypeScript modules provide a mechan
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2 Basic Concepts The remainder of t
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Each enum declaration has a declara
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When an identifier is resolved as a
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which infers the type of 'x' to be
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The only possible values for the Vo
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interface Array { length: number; [
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3.4 Union Types Union types represe
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3.5 Type Parameters A type paramete
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3.6 Named Types Classes, interfaces
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3.7.1 Predefined Types The any, num
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TypeMember: PropertySignature CallS
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3.7.8 Constructor Type Literals A c
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3.8.2 Call Signatures A call signat
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RestParameter: ... Identifier TypeA
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IndexSignature: [ Identifier : stri
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Type aliases are referenced using t
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o o If each type in U has an appare
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o o o M is a non-specialized call o
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3.10.5 Contextual Signature Instant
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interface List { data: T; next: Lis
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4.3 Identifiers When an expression
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of the object literal includes a nu
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A super call invokes the constructo
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( id ) => { ... } ( id ) => expr Th
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A dot notation property access of t
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If func is of type Any, or of an ob
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An example: signature are fixed, an
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This rule means that the call to 'f
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4.14.4 The delete Operator The 'del
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Any Boolean Number String Other Any
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where ??= is one of the compound as
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4.18 The Comma Operator The comma o
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function foo(x: number | string) {
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function processValue(value: number
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5 Statements This chapter describes
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BindingProperty: Identifier Initial
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Similarly, an array destructuring d
Page 101 and 102: 5.5 Continue Statements A 'continue
Page 103 and 104: 6 Functions TypeScript extends Java
Page 105 and 106: function f(x: number) { if (x
Page 107 and 108: When the output target is ECMAScrip
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Page 112 and 113: An interface has the members specif
Page 114 and 115: interface Document { createElement(
Page 117 and 118: 8 Classes TypeScript supports class
Page 119 and 120: The following constraints must be s
Page 121 and 122: Private and protected accessibility
Page 123 and 124: interface A { x: number; f: () => v
Page 125 and 126: ConstructorOverloads: ConstructorOv
Page 127 and 128: BaseClass.apply(this, arguments); a
Page 129 and 130: Initializer expressions for instanc
Page 131 and 132: var x = A.create(); // new A() var
Page 133 and 134: MemberVariableAssignments is a sequ
Page 135 and 136: In addition, the '__extends' functi
Page 137 and 138: 9 Enums An enum type is a distinct
Page 139 and 140: An identifier or property access th
Page 141: var Color; (function (Color) { Colo
Page 144 and 145: If the declaration of 'M' above had
Page 146 and 147: module A { export interface X { s:
Page 148 and 149: module outer { var local = 1; expor
Page 150 and 151: where ModuleName is the name of the
Page 154 and 155: that source file is considered an e
Page 156 and 157: Unlike a non-instantiated internal
Page 158 and 159: import g = require("./geometry"); v
Page 160 and 161: 12.1.3 Ambient Class Declarations A
Page 162 and 163: An ExternalImportDeclaration in an
Page 164 and 165: PrimaryType: ParenthesizedType Pred
Page 166 and 167: ParameterList: RequiredParameterLis
Page 168 and 169: UnaryExpression: ( Modified ) … <
Page 170 and 171: ClassExtendsClause: extends ClassTy
Page 172 and 173: ModuleBody: ModuleElements opt Modu
Page 174 and 175: AmbientClassBodyElements: AmbientCl
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TypeScript Language Specification v1.5

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