Typescript/Types

created : 2020-04-07T11:33:02+00:00
modified : 2020-04-08T03:53:07+00:00

Boolean

let isDone: boolean = false

Number

let decimal: number = 6;
let hex: number = 0xf00d;
let binary: number = 0b1010;
let octal: number = 0o744

String

let color: string = "blue";
color = 'red';

let fullName: string = `Bob Bobbingto`;
let age: number = 37;
let sentence: string = `Hello, myname is ${ fullName }.

I'll be ${ age + 1 } years old next month.`;

Array

let list: number[] = [1, 2, 3];

let list: Array<number> = [1, 2, 3];

Tuple

let x: [string, number];

x = ["hello", 10];

console.log(x[0].substr(1));

Enum

enum Color { Red, Green, Blue }
let c: Color = Color.Green;

enum Color { Red = 1, Green, Blue }
let c: Color = Color.Green;

let colorName: string = Color[2];

alert(colorName); // Green

Any

let notSure: any = 4;
notSure = "it may be string";
notSure = true;

Void

function warnUser(): void {
	alert("This is my warning message");
}

let unusable: void = undefined;
let unusable2: void = null;

Null & Undefined

let u: undefined = undefined;
let n: null = null;

Never

function error(message: string): nver {
	throw new Error(message);
}

function fail() {
	return error("Something failed");
}

function infiniteLoop(): nber {
	while (true) {
	}
}

Type assertions

let someValue: any = "this is a string";

let strLength: number = (<string>someValue).length;


let someValue: any = "this is a string";
let strLength: number = (someValue as string).length;