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@yogain123
Created August 17, 2019 17:49
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TypeScript
@yogain123
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Code

class check{
    flag: boolean = false;
    static countryStatic: string = "INDIA STATIC";
    static countryStaticMethod(){
      console.log("COUNTRY STATIC METHOD CALLED")
    }
    constructor(public name:string){
      this.hola();
    }

    printLogCheck(){
        return "saxena parent";
    }

    hola(){
      console.log("hola parent");
    }
}

class main extends check{
    constructor(public age: number,name: string){
        super(name)
    }

    printLogMain(){
        let lastName = this.printLogCheck();
        let firstName = this.printLogCheck();
        console.log("yogendra "+lastName);
        console.log(firstName);
        super.hola();
        console.log(this.flag);
        let obj = {name:"yogendra",age:25,address:{
          pincode:208022,
          country:"india"
        }}

        let newObj = {...obj.address,city:"bangalore"};
        console.log(obj);
        console.log(newObj);
    }

    
    printLogCheck(){  // overriding
        return "saxena child";
    }

    hola(){
      console.log("hola child");
    }
}

let mainData  = new main(25,"yogendra");
console.log(mainData)
console.log(mainData.printLogMain());
console.log(check.countryStatic);
console.log(check.countryStaticMethod());

@yogain123
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yogain123 commented Aug 26, 2019

Code

https://repl.it/@yogain19/TypeScript

class check{
    flag: boolean = false;
    static countryStatic: string = "INDIA STATIC";
    static countryStaticMethod(){
      console.log("COUNTRY STATIC METHOD CALLED")
    }
    constructor(public name:string){
      this.hola();
    }

    printLogCheck(){
        return "saxena parent";
    }

    hola(){
      console.log("hola parent");
    }
}

function printLog(message: string){
   console.log(message);
    return function (target: any, propertyKey: string, desc: PropertyDescriptor) {
        console.log(desc.value);
        desc.value = function(){
          console.log("printLogMain function changed by Decorator");
        }
    }
}

function logMe(target: any, propertyKey: string, desc: PropertyDescriptor){
  console.log("Log me Log me");
}


function logMeWithParams(msg: string){
  return function(target: any, propertyKey: string, desc: PropertyDescriptor){
  console.log(msg);
}
}

class main extends check{
    constructor(public age: number,name: string){
        super(name)
    }

    @printLog("This is a log message")
    @logMe
    @logMeWithParams("Log me Log me With Params")
    printLogMain(){
        let lastName = this.printLogCheck();
        let firstName = this.printLogCheck();
        console.log("yogendra "+lastName);
        console.log(firstName);
        super.hola();
        console.log(this.flag);
        let obj = {name:"yogendra",age:25,address:{
          pincode:208022,
          country:"india"
        }}

        let newObj = {...obj.address,city:"bangalore"};
        console.log(obj);
        console.log(newObj);
    }

    
    printLogCheck(){  // overriding
        return "saxena child";
    }

    hola(){
      console.log("hola child");
    }
}

abstract class hola{
  constructor(public holaName: string){

  }
  abstract find(holaAge: number): void;
}

interface Address<T, V, P>{
  city: P | V,
  state: V,
  pincode: T | V,
  country?: string | number
}

class holaCheck extends hola{
  constructor(public city: string, holaName: string){
    super(holaName)
  }

  find(holaAge: number){
    console.log("I am Printing hola Age ",holaAge);
  }

  findAddress(address: Address<number, string, boolean>){
    console.log(address.city);
    console.log(address.pincode);
  }

}

let holaCheckInstance = new holaCheck("bangalore", "yogendra");

const address = {
  city: "bangalore",
  pincode: 208022,
  state: "Karnataka",
  hola:"useless Data"
}
console.log(holaCheckInstance.findAddress(address));

type Drink = [string, number];

class Gen<T, P>{
  drink1: Drink = ["yogendra", 25];
  drink2 = ["yogendra", 25] as Drink;   // Type assestion
  constructor(public name: P, public age: T){

    let address = {city:"bangalore", state:"Karnataka", pincode:"222222"};
    let add1: Address<string, string, string> = address;
    let add2 = address as Address<string, string, string>;   // Type Assertion
    console.log(add1.city);
  }

}

let gen = new Gen<number, string>("yoyoyo",26);
console.log(gen)

let mainData  = new main(25,"yogendra");
console.log(mainData)
console.log(mainData.printLogMain());
console.log(check.countryStatic);
console.log(check.countryStaticMethod());


generic around functions

Screen Shot 1941-06-06 at 1 28 01 AM

@yogain123
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Incorrect

class Person{
  constructor(public age?: number, public name: string){
    
  }
}

Error : [typescript] A required parameter cannot follow an optional parameter.

@yogain123
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enums

Screen Shot 1941-06-06 at 12 56 59 AM



Screen Shot 1941-06-06 at 12 54 41 AM

you can access enum as you access object, It automatically gets converted to object in js

@yogain123
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type assertion

we tell TS that we are a developer and we know better what's going on, ==> it override the default type assertion behaviour of TS

enum yoyo  {
  name = "yogendra"
}


let uu: string = yoyo.name;
let pp = yoyo.name as string;

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yogain123 commented Nov 1, 2019

interface Person{
    name:string,
    [id: string]:{
        pincode: number,
        country: string
    }
}

let p: Person = {
    name:"yogendra",
    "12A":{
        pincode:208022,
        country:"india"
    },
    "13A":{
        pincode:208022,
        country:"india"
    },
    "14A":{
        pincode:208022,
        country:"india"
    }
}

class Person<T,S>{
    constructor(public name:T, public age:S){
    }

    sum<T>(firstName: T){
        console.log(firstName);
    }
}

let p = new Person<string, number>("yogendra",25);
p.sum("yogendra");
p.sum<string>("saxena")

@yogain123
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function type

both are correct ways:

Screen Shot 1941-08-11 at 2 05 20 PM

@yogain123
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implements

  • interface/type extends interface/type (can extends multiple interface/ types)
  • class extends class (can extends only one class)
  • class implements interface/types (can implements multiple interface/types)

Screen Shot 1941-08-11 at 2 32 03 PM

@yogain123
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extra

type Choise = "A" | "B" | "C";
let p : Choise = "A"


type testType = keyof {id: "test", age: 2} ;   // ==> testType : id | age
let t: testType = "age"

interface MyInterface {
    name: string;
}

interface MyInterface {
    age: number;
}

let box: MyInterface = {   // box will be of type ==> {name:string, age: number}
    name:"yogendra",
    age:34
}
    

@yogain123
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multiple inheritance

multiple inheritance is not supported in TS, but it is done using interface

interface Person {
    pow: (a: number)=>number
}

interface Vehicle {
    pow: (a: number)=>number
}

class Body1 implements Person, Vehicle{
    personName="done";
    pow(a:number): number{
        return a*a;
    }
}

class Body2 implements Person, Vehicle{
    personName="done";
    pow(a:number): number{
        return a*a*a;
    }
}

console.log(new Body1().pow(2));   //4
console.log(new Body2().pow(2));  //8

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yogain123 commented Jan 24, 2020

interface, types, enum syntax

interface Person{
    name:string;
    age:number
}

type Address = {
    pincode:number
    country:string
}

type Drink = string | number;
type Boy = [string, boolean];

interface Status{
    position:string;
    experience: number
}

enum Colors{
    b="blue",
    g="green"
}

console.log(Colors.b);   // blue

function getName(name:string) {
    return {
        name,
        age:25
    } as const
}

class Test implements Person, Status, Address{
    constructor(public name:string,public age:number, public position:string,public experience:number,
        public pincode:number, public country:string){
        
    }
}

@yogain123
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decorator

Screenshot 2020-01-24 at 12 41 20 PM

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yogain123 commented Nov 7, 2022

@yogain123
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yogain123 commented Nov 8, 2022

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