variable Deno.exitCode
The exit code for the Deno process.
If no exit code has been supplied, then Deno will assume a return code of `0`.
When setting an exit code value, a number or non-NaN string must be provided,
otherwise a TypeError will be thrown.
```ts
console.log(Deno.exitCode); //-> 0
Deno.exitCode = 1;
console.log(Deno.exitCode); //-> 1
```
number