basic-types.md

my-awesome-typescript-project

---

my-awesome-typescript-project / src/basic-types

src/basic-types

Basic types.

Table of contents

• 1. Object shapes
• 2. Object implementations
• 3. Literal types

1. Object shapes

objectShape

Defined in: src/basic-types.ts:18

Simple interface

Remarks

• Defines object shape: properties names, types, order, optionality.
• Interfaces can be modified after creation but this should never be done.

Extended by

• extendedShape

Properties

Property	Type	Defined in
one	string	src/basic-types.ts:19
two?	number	src/basic-types.ts:20
three	(s) => number	src/basic-types.ts:21
four	(s) => string	src/basic-types.ts:22

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extendedShape

Defined in: src/basic-types.ts:34

Extended interface

Remarks

• Shows how the extend clause is used declaratively in typescript.
• Properties accept a readonly modifier.
• A single interface can extend multiple interfaces (separated with commas).

Extends

• objectShape

Properties

Property	Modifier	Type	Inherited from	Defined in
one	public	string	objectShape.one	src/basic-types.ts:19
two?	public	number	objectShape.two	src/basic-types.ts:20
three	public	(s) => number	objectShape.three	src/basic-types.ts:21
four	public	(s) => string	objectShape.four	src/basic-types.ts:22
five	readonly	symbol	-	src/basic-types.ts:35

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extendedType

type extendedType = extendedType;

Defined in: src/basic-types.ts:46

Extended type

Remarks

• Equivalent of extending an interface, actually intersection type of both constituents.
• Reminder: a subtype always have more or more specific properties than its supertype.

---

derivedShape

Defined in: src/basic-types.ts:57

Create interface from implementation

Remarks

• This pattern can be used to extend built-in objects and override their methods.

Extends

• objectClass

Properties

Property	Modifier	Type	Inherited from	Defined in
five	readonly	symbol	-	src/basic-types.ts:58
one	public	string	objectClass.one	src/basic-types.ts:101
two	public	number	objectClass.two	src/basic-types.ts:102
three	public	(s) => number	objectClass.three	src/basic-types.ts:103

Methods

four()

four(s): string;

Defined in: src/basic-types.ts:110

Parameters

Parameter	Type
s	string

Returns

string

Inherited from

objectClass.four

2. Object implementations

objectLiteral

const objectLiteral: objectShape;

Defined in: src/basic-types.ts:67

Simple object literal

Remarks

• The object keys and values conform to the interface.

---

derivedLiteral

const derivedLiteral: derivedShape;

Defined in: src/basic-types.ts:80

Derived object literal

Remarks

• Same as export const derivedLiteral: objectShape & extendedShape.

---

objectClass

Defined in: src/basic-types.ts:100

Simple class

Remarks

• The class implements the interface.
• Important: interface properties define public contracts only.
• An alternative is to use the interface to declare getters and setters of private properties.
• Reminder: public, private, protected and readonly modifiers are typescript only and not supported by native ECMA.
• When in doubt, refer to the list of ECMA reserved words for javascript.
• Personal note : the following interpretation involuntarily makes a case for using functional programming over classes.

Extended by

• derivedShape
• derivedClass

Implements

• objectShape

Constructors

Constructor

new objectClass(): objectClass;

Defined in: src/basic-types.ts:104

Returns

objectClass

Properties

Property	Type	Defined in
one	string	src/basic-types.ts:101
two	number	src/basic-types.ts:102
three	(s) => number	src/basic-types.ts:103

Methods

four()

four(s): string;

Defined in: src/basic-types.ts:110

Parameters

Parameter	Type
s	string

Returns

string

Implementation of

objectShape.four

---

derivedClass

Defined in: src/basic-types.ts:124

Derived class

Remarks

• Illustrates ECMA extends vs typescript implements.
• Overridden methods have to be identified and cannot violate the superclass types.
• super.someMethod() can be used in overriden methods to access superclass method.

Extends

• objectClass

Implements

• extendedShape

Constructors

Constructor

new derivedClass(): derivedClass;

Defined in: src/basic-types.ts:126

Returns

derivedClass

Overrides

objectClass.constructor

Properties

Property	Type	Inherited from	Defined in
one	string	extendedShape.one objectClass.one	src/basic-types.ts:101
two	number	extendedShape.two objectClass.two	src/basic-types.ts:102
three	(s) => number	extendedShape.three objectClass.three	src/basic-types.ts:103
five	symbol	-	src/basic-types.ts:125

Methods

four()

four(s): string;

Defined in: src/basic-types.ts:131

Parameters

Parameter	Type
s	string

Returns

string

Implementation of

extendedShape.four

Overrides

objectClass.four

3. Literal types

literal

const literal: {
  a: 0;
  b: "union";
};

Defined in: src/basic-types.ts:148

Create literal type from implementation

Type Declaration

Name	Type	Default value	Defined in
a	0	0	src/basic-types.ts:148
b	"union"	-	src/basic-types.ts:148

Remarks

• Converting an object to a literal type using as const makes all its properties read-only.