The TypeScript Cheat Sheet

This "cheat sheet" was originally taken from an excellent article on Site Pen. We made a copy of it here in github because it is a great way to maintain this cheat sheet and keep it up-to-date.

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Last updated for: TypeScript 0.9.5

Primitive Types

Concept	Code
Any type (explicitly untyped)	any
void type (null or undefined, use for function returns only)	void
String	string
Number	number
Boolean	boolean

Named types (interface, class, enum)

Concept	Code
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

Concept	Code
Object with implicit Any properties	{ foo; bar; }
Object with optional property	{ required:Type; optional?:Type; }
Hash map	{ [key:string]:Type; }

Arrays

Concept	Code
Array of strings	string[] or Array<string>
Array of functions that return strings	{ ():string; }[] or Array<()=>string>

Functions

Concept	Code
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

Concept	Code
Function using type parameters	<T>(items:T[], callback:(item:T) => T):T[]
Interface with multiple types	interface Pair&lt;T1, T2&gt; {

  | `first:T1;`
  | `second:T2;`
  | `}`

Constrained type parameter | <T extends ConstrainedType>():T

Other

Concept	Code
Type of a variable	typeof varName