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I know that in JS point is a decimal mark and I see that there's a comma between 1 and 5, but why does (1,5 - 1) equal to 4 and what happens with 1, in the beginning of the state

Artem Kuroptev
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  • `1,5` is not one number. It's actually three things: the number `1`, a comma and the number `5`. So: `(1,5 - 1)` = `(1, 5 - 1)` = `(1, 4)` and the `1` is thrown away so the result of this expression is `4`. – Jesper Apr 26 '22 at 08:55
  • [JavaScript Comma Operator](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Comma_Operator) – Usama Apr 26 '22 at 08:56
  • I don't understand why you don't use 1.5 but use 1,5 – Minh Viet Apr 26 '22 at 09:00
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    @MinhViet: Some languages use `,` as decimal separator. OP was probably curious how/why the expression still produced a result. – Felix Kling Apr 26 '22 at 09:07
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    @MinhViet, I was solving some js-knowledge tests when i got the task. – Artem Kuroptev Apr 26 '22 at 11:21
  • @Jesper, That's exactly what I described in question. I want to know why `1` is thrown away from `(1, 4)`. I mean it is obvious that `(1, 5 - 1)` equal to `(1, 4)`. The point is why `(1, 4)` equals to `4` – Artem Kuroptev Apr 26 '22 at 11:22
  • It is the [comma operator](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Comma_Operator). By itself it's not useful, but it is useful, for example, to initialize multiple variables in a `for` statement. – Jesper Apr 26 '22 at 13:11

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