Typescript 101

What typescript is?

Typescript is a superset of javascript. Any valid javascript code also valid typescript code.

Typescript has strong typing, Object-oriented, Compile-time errors. Typescript can’t directly run on a browser, it has to transpile to ES5 javascript.

How can we install typescript on our machine.

// Mac
sudo npm install -g typescript 

All typescript code file has to be end with .ts extension.

Let get started. 

// const vs let
const cannotChange = 10;
let canChange = 'abc';

// Type
// by default, typescript variables has to specifi a type on each variable

// Number
let decimal: number = 10;
let hex: number = 0xf00d;

// String
let person: string = "john";
let age: number = 30;

// Array
let data: number[] = [ 1, 2, 3 ];

// Boolean

let isEdit: boolean = true;
let done: boolean = false;

//Tuple
let x: [string, nubmer];
x = ["hi", 1]; // ok
x = [11, lol]; // Error

//Function
function greeting(person: string) {
  return `hello, ${person}`;
}

// Interface
interface Person {
  firstName: string;
  lastName: string;
}
function greeting(person: Person) {
  return `hello, my name is: ${person.firstName} ${person.lastname}`;
}
let user = {
 firstName: "John",
 lastName: "Smith",
};
console.log(greeting(user));

// Classes
class Student {
    fullName: string;
    constructor(public firstName, public middleInitial, public lastName) {
        this.fullName = `${firstName} ${middleInitial} ${lastName}`;
    }
}

interface Person {
    firstName: string;
    lastName: string;
}

function greeter(person : Person) {
    return `Hello, ${person.firstName} ${person.lastName}`;
}

let user = new Student("Jane", "M.", "User");
console.log(greeter(user));