> type guard

Thanks for the link, I am currently doing something similar without knowing TS implicit behavior.

With 1st given example in the link, I forced on a style to such:

```

function doSomething(x: number | string) { if (typeof x === 'string') { doSomethingForString(x) }

  // Never do catch all to assume all non-strings are numbers
  if (typeof x === 'number') {
    doSomethingForNumber(x)
  }

  // Per transpiler rule, you not meant to be here, so error throwing is appropriate
  throw new Error('Unexpected type')

}

function doSomethingForString(x: string) { // Code }

function doSomethingForNumber(x: number) { // Code }

```