Typescript-101 Flashcards
What is the diff b/w let, var & const?
Var will create a global variable and it is availabel in Global Object
Let will create a global variable, but does not belong to Global Object
Const will create a global Constant and it is not a property of Global Object
What is the advantage of let?
With let you can create block level vars
What is the advantage of const?
const requires intiallization and must not change while time
Can we define objects with let
Yes
Ca we define html templates with let
Yes A good way to do that
How can you define template literals with let?
let obj = {
name : "kjskj
}"
let templateStr = “Name is” + $(obj.name)
What is arrow function?
Arrow function is one way of writing inline function, like
var sum = (a,b) => { return a+b;}
var sum = (a,b) => a+b;
Does Arrow function retains the Lexical scope of this?
YEs
Write code for a class and constructor?
Class Person {
constructor(name) { // need not define the as var or let
this.name = name;
}
}
Do you add access modifer or return type in function or construtors?
Nope straight to name
How can you extend the class ?
Using keyword extends and use super where required
How can we create an obj of a class?
let obj = new Employee(“sdfsfdee”);
What is Object.create
To do prototypical inheritance without using constructor function
What is the public access modifier?
Use export
What is import do?
To import any exported entity
How can you import everthing ?
import * as item from “./mod.js”
Give one example of how the typesscript code looks in JS form?
class Greeter {
greeting : string;
constructor(message: string){
this.greeting: message;
}
greet(){
return “Greet”
}
let greeter = new Greeter(“Greeter”);
}
The above looks below in JS:
var Greeter = (function(){
function Greeter(message){
this.greeting = message;
}
Greeter.prototype.greet = function(){
return “Greet”;
}
return Greeter; // So i JS you can return the obj in the class itself as we do in JAVA
}());
How do you define a String type in TS?
message: string;
Do we require to specify the function keyword to start a function?
Need not
How many Primitive types we have in TS?
string, Number, Boolean, undefined, null
What all format des Number supports?
Float and int, also it supports Hexadecimal, Octal, decimal, binary
How do you define the variable , variabetype , variablename & variablevalue?
let fName: string = ““myname””;
What is the diff b/w null & undefined?
undefined means the value has not been defined, null means it has defined the object & that object is null.
Do we have Array, Enum, Any & Void in TS
Yes we have
How do you define an array
var listnum:number[] = [20,40];
How do you make one Any type var ?
let me; Or var me;
How do you define enums?
enum Cards{DIAMOND, SPADE};
var c = Cards.DIAMOND;
c= 1;// Cards.DIAMOND;How can I define a function with a function keyword?
function getData(mesaage): void{
//do some
}How do define an interface?
interface myInterface {
greetUser(message: string): void;
}
How can we implement and interface?
class implClass implements myInterface {
greetUser(msg: string){
return “name”;
}
}
How will you aceess the methods of a class?
function(greet: GreeterClass){
greet.greetUser("Hello");
}What is the default access modifer?
public
Which keyword helps in instantiating a class?
new
How can you define an anonymous function?
let myFunct = function(message: string) {return message};
How can we pass a default value to a function argument?
function me(message: string =”hello”){
}
