addmehdi.js

function hello(name) {
    console.log("Hello " + name);
}
var firstName = "bob";
hello(firstName);
hello(firstName + " marley");
function concat(a, b) {
    return a + b;
}
var wcs = concat("Wild", concat("Code", "School"));
console.log(wcs);

addmehdi.ts

function hello(name: string) {
    console.log("Hello " + name);
}

var firstName : string = "bob";

hello(firstName);
hello(firstName + " marley");

function concat(a : string, b : string) : string{
    return a + b;
}

var wcs : string = concat("Wild", concat("Code", "School"));
console.log(wcs);