Example of simple TypeScript

Calculator.ts

function sumAndDisplay(left : number, right : number, prefix : string  = "Result") {
    var result = left + right;
    alert(`${prefix}: ${result}`);
}

sumAndDisplay(1, 2);

Filter.ts

function filter<T>(items : T[], predicate : (x : T) => boolean) : T[] {
	var filtered = [];
	for(let x of items){
		if(predicate(x)){
			filtered.push(x);
		}
	}
	return filtered;
}

interface IPerson {
	active : boolean;
	name: string;
}

let people : IPerson[] = [
	{ active: true, name: "Peter" },
	{ active: false, name: "Olle" },
	{ active: true, name: "Isabelle" }
];

let activePeople = filter(people, p => p.active);
alert(activePeople.length);