typescript_cheatsheet.adoc

TypeScript Cheat Sheet

Based on Sitepen’s TypeScript Cheat Sheet

Table 1. TypeScript cheatsheet

1	2
Build script language
Any type (explicitly untyped)	any
String	string
Number	number
Boolean	boolean
Named types (interface, class, enum)
Interface	interface IChild extends IParent, SomeClass { property:Type; optionalProp?:Type; optionalMethod?(arg1:Type):ReturnType; }
Class	class Child extends Parent implements IChild, IOtherChild { property:Type; defaultProperty:Type = 'default value'; private _privateProperty:Type; static staticProperty:Type; constructor(arg1:Type) { super(arg1); } private _privateMethod():Type {} methodProperty:(arg1:Type) => ReturnType; overloadedMethod(arg1:Type):ReturnType; overloadedMethod(arg1:OtherType):ReturnType; overloadedMethod(arg1:CommonT):CommonReturnT {} static staticMethod():ReturnType {} subclassedMethod(arg1:Type):ReturnType { super.subclassedMethod(arg1); } }
Enum	enum Options { FIRST, EXPLICIT = 1, BOOLEAN = Options.FIRST | Options.EXPLICIT }
Object type literals
Object with implicit Any properties	{ foo; bar; }
Object with optional property	{ required:Type; optional?:Type; }
Hash map	{ [key:string]:Type; }
Arrays
Array of strings	string[] or Array<string>
Array of functions that return strings	{ ():string; }[] or Array<() ⇒ string>
Functions
Function	{(arg1:Type, argN:Type):Type; } or (arg1:Type, argN:Type) => Type;
Constructor	{ new ():ConstructedType; } or new () ⇒ ConstructedType;
Function type with optional param	(arg1:Type, optional?:Type) ⇒ ReturnType
Function type with rest param	(arg1:Type, …​allOtherArgs:Type[]) ⇒ ReturnType
Function type with static property	{ ():Type; staticProp:Type; }
Default argument	function fn(arg1:Type = 'default'):ReturnType {}
Arrow function	(arg1:Type):ReturnType => {} or (arg1:Type):ReturnType => Expression
Generics
Function using type parameters	<T>(items:T[], callback:(item:T) ⇒ T):T[]
Interface with multiple types	interface Pair<T1, T2> { first:T1; second:T2; }
Constrained type parameter	<T extends ConstrainedType>():T
Other
Type of a variable	typeof varName