example: how to easily run any TypeScript code on your command line

test.ts

#!/usr/bin/env ts-node

/*
You can run simple scripts in TypeScript without compiling or any other other
additional steps!

	npm i -g typescript ts-node
	chmod 755 test.ts
	./test.ts

You can also test small code snippets on the command line: 
  ts-node -p "1+1"

Unfortunately I couldn't get the REPL to work.
  ts-node 
  > 1+1
Thrown: ⨯ Unable to compile TypeScript
[eval].ts: Cannot find name 'exports'. (2304)
[eval].ts (0,11): Cannot find name 'module'. (2304)

*/

function foo( x : number ) {
	return x * 2;
}

var y : number = 2;
console.log(`2×${y} = ${foo(y)}`);

// this gives the expected type error at compile time:
// console.log(`2×'a' = ${foo('a')}`);