Typescript.txt

* A superset of javascript created by Microsoft
* Compiles to plain javascript code
* Includes many ES6 features
* Cohesion concept: Things that are related should be part of one unit

Typescript compiler:
----------------------------
* Automatically compiles .ts files to .js files.
* Will be installed with NPM
* Supports ES6 features
* Used by Angular

* We can install typescript with npm as below
npm i -g typescript
* We can run typescript file like below
tsc file-name.ts
* We can execute both TS and JS files at a time as below
tsc file-name.js | node file-name.js (OR)
tsc file-name.js && node file-name.js

* 

Available Types:
---------------------------
* String
* Number
* Boolean
* Null
* Array
* Any
* Void => No return type
* Tuple
* enum Color { Reb = 0, Green = 1, Blue = 2 };


* Object[] => Array of objects
* number[] => Array of numbers
* string[] => Array of strings
* any[] => Array of any






*************************************************************************************
* let aa: number; // this is called 'type annotation'
* let a = 10;
	a = 'hello'; // Gives error = here the type of 'a' is 'number'

* Declaring a type a parameter while defining the function is called "Inline annotation"
Ex 1:
	let drawPoint = (point: number) => {
		console.log(point);
	}

	drawPoint(10);

Ex 2:
	let drawPoint = (point: {x: number, y: number}) => {
		console.log(point);
	}

	drawPoint({
		x: 1,
		y: 5
	});

	Note: we can achieve Ex 2 with interface as well as below

	interface Point {
		x: number,
		y: number
	}

	let drawPoint = (point: Point) => {
		console.log(point);
	}

	drawPoint({
		x: 1,
		y: 5
	});

	Note: The first word of name of the interface should be capital (Pascal case)


* let b; // here the type of 'b' is 'any'

* Type assertion concept:
	Type assertion means...
	let message;
	message = 'abc';
	let endsWithC = (<string>message).endsWith('c');
	let alternativeWay = (message as string).endsWith('c');

* 




* Class example:
class Point{

	// private x: number;
	// private y: number;

	constructor(private x?: number, private y?: number){
		// this.x = x;
		// this.y = y;
	}

	draw(){
		console.log('X: '+this.x+', Y: '+this.y);
	}
}

// To create an object follow as below
	let point: Point = new Point(1, 2); (OR) let point = new Point(1, 2);
	point.draw();




*************************************************************************************
IMP points to remember:
---------------------------------
* No need to specify 'function' keyword while creating a function
* Interfaces are purely for declarations
* To execute .ts file and .js at once, follow below command
	tsc filename.ts | node filename.js (OR) tsc filename.ts && node filename.js

* tsc *.ts --target ES5 && node main.js

* Once we make a parameter optional all the other parameters on the right side parameters should also optional.











*************************************************************************************
Interview things:
-------------------------------------------------------------------------------------
* https://www.youtube.com/watch?v=TlhxEYXifDw










*************************************************************************************
Useful site:
---------------------------------
* https://www.tutorialsteacher.com/typescript/