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Bu materyal This madde henüz sadece: English, 한국어 dillerinde mevcuttur. Lütfen bize bu bölümün çevirisini Türkçe çevirmek için yardım ediniz.

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.