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## While hangi değerleri gösterir?

önem: 4

Her döngü için ekranda gösterilecek değerler nelerdir? Bu değerleri yazın ve sonra cevap ile karşılaştırın.

Her iki döngüde de `alert` aynı değerleri mi gösterir?

Both loops `alert` same values or not?

1. Önden eklemeli `++i`:

``````let i = 0;
while (++i < 5) alert( i );``````
2. Sonradan ekelemeli form `i++`

``````let i = 0;
while (i++ < 5) alert( i );``````

The task demonstrates how postfix/prefix forms can lead to different results when used in comparisons.

1. From 1 to 4

``````let i = 0;
while (++i < 5) alert( i );``````

The first value is `i = 1`, because `++i` first increments `i` and then returns the new value. So the first comparison is `1 < 5` and the `alert` shows `1`.

Then follow `2, 3, 4…` – the values show up one after another. The comparison always uses the incremented value, because `++` is before the variable.

Finally, `i = 4` is incremented to `5`, the comparison `while(5 < 5)` fails, and the loop stops. So `5` is not shown.

2. From 1 to 5

``````let i = 0;
while (i++ < 5) alert( i );``````

The first value is again `i = 1`. The postfix form of `i++` increments `i` and then returns the old value, so the comparison `i++ < 5` will use `i = 0` (contrary to `++i < 5`).

But the `alert` call is separate. It’s another statement which executes after the increment and the comparison. So it gets the current `i = 1`.

Then follow `2, 3, 4…`

Let’s stop on `i = 4`. The prefix form `++i` would increment it and use `5` in the comparison. But here we have the postfix form `i++`. So it increments `i` to `5`, but returns the old value. Hence the comparison is actually `while(4 < 5)` – true, and the control goes on to `alert`.

The value `i = 5` is the last one, because on the next step `while(5 < 5)` is false.