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TypeScript

Tutorial web site

TypeScript

Important commands​

yarn install -g typescript # install
tsc --v # version
npm install -g ts-node # ts to js converter

tsc app.ts compiles to code to js file node app.js runs the js file ts-node app.ts run ts file directly

Types​

  • Primitive types String number boolean null undefined symbol - constant
  • Object Type

let newString: string = 'Hello world';

const newNumber: number = 1;

let newBool: boolean = true;

let newArray: number[] = [1, 2, 3, 4];

let newFuctionVariable: (name: string) => string;
newFuctionVariable = function(name: string) {
  return `Hi ${name}`;
}; // this is valid
// this is invalid cause we are assigning wrong data function to the variable
// newFuctionVariable = function() {
//   console.log('Hello');
// }; 
console.log('This is a String : ' + newString);
console.log('This is a Number : ' + newNumber);
console.log('This is a Boolean: ' + newBool);
console.log('This is a Array: ' + newArray);

//Object
let employee: { 
firstName: string;
lastName: string;
age: number;
jobTitle: string;
};

let big: bigint = 9007199254740991n; //bigint
//In typescript numbers are floting point and bigint are long in java

//String literals
``let profile: string = `I'm ${firstName}.  I'm a ${title}`;``
``let description = `This TypeScript string can  span multiple  lines `;``

Contextual typing​

document.addEventListener('click', function (event) { console.log(event.button); // });

Tuple​

  • Tuple is Final list.
let skill: [string, number]; 
skill = ['Programming', 5];

// Optional parameters
let bgColor, headerColor: [number, number, number, number?];

Enum​

enum name {constant1, constant2, ...};