Create GUID in TypeScript - function is valid in JS but not TS

Question

I'm trying to use the solution posted here to create a GUID-type string in my angular4/TypeScript web app.

Here is the function I'm writing:

function uuidv4() {
  return ([1e7]+-1e3+-4e3+-8e3+-1e11).replace(/[018]/g, c =>
    (c ^ crypto.getRandomValues(new Uint8Array(1))[0] & 15 >> c / 4).toString(16)
  )
}
console.log(uuidv4())

TypeScript is giving me the following error:

Operator '+' cannot be applied to types 'number[]' and '-1000'.

What do I need to change to make this TS compatible?

Thanks!

I suppose the error points to another location in your code. Search for "-1000" — hgoebl, Jul 20 '17 at 08:30
I second that what @hgoebl has said. The issue is somewhere else. https://plnkr.co/edit/MxwthKjqxCWRAicGtcXV. Please provide andular2 code. — The Hungry Dictator, Jul 20 '17 at 08:39
@hgoebl - when I remove the function the code compiles beautifully, so the problem has to be within the function. As specified, I'm using Angular 4, with TS version 2.2.2 . VS code is running version 2.3.2. — Basya Rosemann, Jul 20 '17 at 08:45
Also, the following chars are highlighted in my editor (vs code): `[1e7]+-1e3`. Can it be a TS version issue? — Basya Rosemann, Jul 20 '17 at 08:48
OK, I see. Seems like TS compiler internally converts -1e3 to -1000. If you want to get rid of the problem quickly, just replace the thing before `.replace` with `'10000000-1000-4000-8000-100000000000'` — hgoebl, Jul 20 '17 at 08:53
@hgoebl - Huh. Can you please explain why TS does this and how this works? — Basya Rosemann, Jul 20 '17 at 10:10
You can generate unique values by new Date().getTime().toString() + Math.random().toString().split(".")[1] Just a thought — Kamran, Sep 20 '19 at 02:19

score 9 · Accepted Answer · answered Jul 20 '17 at 13:03

If you want to leave the somehow cryptic code (a puzzle?) almost as it's ingenious original but TypeScript compatible, you could use:

function uuidv4(): string {
  return (''+[1e7]+-1e3+-4e3+-8e3+-1e11).replace(/[018]/g, ch => {
      let c = Number(ch);
      return (c ^ crypto.getRandomValues(new Uint8Array(1))[0] & 15 >> c / 4).toString(16)
    }
  )
}

Unscrambled:

[1e7]+-1e3+-4e3+-8e3+-1e11 produces the string 10000000-1000-4000-8000-100000000000 and saves an unbelievable amount of characters ;-)
TypeScript is not aware that the expression is intended to produce a string. (This could be regarded as bug IMHO.)
When you start the expression with '' +, type inference detects the expression as string and compiler now accepts concatenating the array with the numbers. A more readable form would be '' + 1e7 + -1e3 + -4e3 + -8e3 + -1e11, because then you no longer need the [] to treat the + operators as string concatenation instead of a numeric addition.
The next problem arises with the auto-coercion of c from string to number. For this, I've added an explicit conversion from ch as string to c as number.

That's another proof that "just rename your *.js files to *.ts and you have valid TypeScript" is not true in all cases. I'm still convinced that using TypeScript pays off very soon and such small changes do not cost much.

Create GUID in TypeScript - function is valid in JS but not TS

1 Answers1