February 2015
Intermediate to advanced
664 pages
24h 26m
Polish
Content preview from Programowanie w JavaScript Rusz głową!
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320
Rozdział 7.
Prawda i fałsz
JavaScript uwzględnia fałsz
Jeszcze raz przypominamy, że zrozumienie tego, co będzie uznawane za
prawdę, a co za fałsz, sprowadza się do zapamiętania, co będzie fałszem
— bo wszystko pozostałe będzie prawdą.
Poniżej przedstawiliśmy pięć wartości, które JavaScript traktuje jak
logiczny fałsz.
Fałszem jest udefined.
Fałszem jest null.
Fałszem jest 0.
Fałszem jest także pusty łańcuch znaków.
Fałszem jest też NaN.
A zatem każde wyrażenie warunkowe przedstawione na poprzedniej stronie
zostanie potraktowane tak, jak gdyby została w nim umieszczona wartość
false
. A czy wspominaliśmy, że każda inna wartość (oczywiście z wyjątkiem ...
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