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TypeScript Cheat Sheet by

TypeScript Quick Reference
development     programming     javascript     web     typescript

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
Type Definition Files

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 {
  productName: string;
  quantity: number;
  price: number;
  orderDate: Date;
  shipped: boolean;
  //Optional
  outOfStock?: boolean;
  //Method
  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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