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TypeScript 2.1.4 Cheat Sheet (DRAFT) by

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Variables

var
Same as ES5 (funct­ion­-sc­oped).
let
Block-­scoped (like ES6).
const
Same as 
let
, but readonly.

Base types

Boolean
 
boolean: true | false
Number
 
number: decimal | hex | binary | octal
String
 
string: '...' | "..."­ | `...${...}...`
Array
 
type[] | type[][] | Array<type>
Tuple
 
[type, type, ...]
Enum
 
enum X { A = 1, B, C, ... };
Any
 
any
Void
 
function f(): void
Null
 
let n: null = null;
Undefined
 
let u: undefined = undefined;
Never
Use for functions, which never ends.
 
--stri­ctN­ull­Checks
- check for assign­ement.

Destru­cturing

Array
 
i = [1, 2];
[f, s] = i;
[f, s] = [s, f];
f([f, s]: [number, number])
[f, s, ...r] = [1, 2, 3, 4];
[f] = [1, 2, 3, 4];
[, s, , f] = [1, 2, 3, 4];
Object
 
o = { a: "­f", b: 1, c: "­b" }
{ a, b } = o;
({ a, b } = { a: "­b", b: 1 });
{ a, ...p } = o;
Property renaming
 
{ a: n1, b: n2 } = o;
{ a, b }: { a: string, b: number } = o;
Default values
 
{ a, b = 1 } = o;
Function declarations
 
f(o: { a: string, b?: number })
Spread
 
let f = [1, 2];
let s = [3, 4];
let b = [0, ...f, ...s, 5];
> [0, 1, 2, 3, 4, 5]
 

Interface

interface LabelledValue {
    ...
}

Optional parameters

name?: <ty­pe>;

Readonly properties

interface Point {
    readonly x: number;
    ...
}
Readon­lyA­rra­y<T>
Variables use const whereas properties use readonly.