TypeScript Cheat Sheet

A Programming › JavaScript cheat sheet in English by GregFinzer

TypeScript Quick Reference

Development Programming JavaScript Web Typescript

64,836 views 16,406 downloads 9 Feb 2017 History

PRs

3.8 avg · 16 ratings

Types

String	let customerName: string= "John Doe";
Number	let price: number = 19.95;
Boolean	let shipped: boolean = false;
Date	let orderDate: Date = new Date(2017, 2, 9);
Any	let something: any = "Can be anything";
Enum	enum Color {Red, Green, Blue};
Array	let cards: string[] = ['Visa', 'MasterCard'];
Null	let orderId: number = null;
Tuple	let stateTaxRates: [string, number];
Void	function log(msg: string): void { console.log(msg); }
Const	const lives: number = 99;

Classes

class OrderLogic {
    constructor(public order: IOrder) {  }

    getOrderTotal(): number {
        let sum: number = 0;

        for (let orderDetail of this.order.orderDetails)
        {
            sum += orderDetail.price;
        }
        return sum;
    }
}

Abstract Classes

abstract class Person {
  name: string;
  monthlySalary: number;
  monthlyBenefits: number;

  abstract calcSalary(): number;
}

Inheritance and Implementing Interfaces

interface IGPS {
  getLocation() number;
}

interface ISelfDrive extends IGPS {
  drive(latitude: number, longitude: number, elevation: number) : void;
}

class Vehicle {
  make: string;
  model:  string;
  year:  number;
}

class FlyingCar extends Vehicle  implements ISelfDrive {
   hasGps: boolean;

  drive(latitude: number, longitude: number, elevation: number)  {
  }

  getLocation(): number {
  }
}

Usage

Installing TypeScript npm	npm install -g typescript
Compiling TypeScript	tsc somefile.ts
TypeScript Docs	TypeScriptLang.org
Type Definition Files	DefinatelyTyped.org

Scope/Modifiers

Public (default)	public firstName: string;
Protected	protected inventory: number;
Private	private outOfStock: boolean;
Read Only	readonly pi: number = 3.14159;
Static	static log(msg: string) { console.log(msg) };

Interfaces

interface IOrderDetail {
&nbsp;&nbsp;productName: string;
&nbsp;&nbsp;quantity: number;
&nbsp;&nbsp;price: number;
&nbsp;&nbsp;orderDate: Date;
&nbsp;&nbsp;shipped: boolean;
&nbsp;&nbsp;//Optional
&nbsp;&nbsp;outOfStock?: boolean;
&nbsp;&nbsp;//Method
&nbsp;&nbsp;calcTax: (taxRate: number) => number;
}

Optional Parameters

class Util {
  log(msg: string, logDate?: Date) {
    if (logDate)
      console.log(logDate + ' ' + msg);
    else
      console.log(new Date() + ' ' + msg);
  }
}

Rest Parameters

class Order {
  addOrderDetails(...orderDetails: IOrderDetail[]) {
  }
}

Namespaces

namespace AcmeCorp.Logging {
  export class Logger {
       static log(msg: string) : void {
        console.log(msg);
      };
  }
}

/// <reference path="AcmeCorp.Logging.ts" />

//Alias
import logger = AcmeCorp.Logging.Logger;

namespace AcmeCorp.OnlineStore {
  class OrderLogic {
    calcOrder(): number {
        logger.log("calculating order");
        return 0;
    }
  }
}

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Comments (3)

nadarajan 22:51 26 Dec 2019

Unable to download!

nadarajan 13:35 21 May 2019

Good!

ramanagbv 05:14 7 May 2018

good