TypeScript example for tooling

tstooling.ts

let myNumber: number = 10;
let myString: string = 'this is a string';

const badMath = (x: number, y: number) => {
  return x * y;
}

badMath(myNumber, myString) /** 
                             * error TS2345: Argument of type 'string' 
                             * is not assignable to parameter of type 'number'.
                             */