April 2025
Intermediate to advanced
324 pages
7h 35m
Portuguese (Portugal, Brazil)
Content preview from Programando o TypeScript
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Capítulo 3. Tudo sobre os tipos
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No último capítulo, introduzi a ideia de sistemas de tipos, mas nunca defini o que significa realmente o tipo em sistema de tipos.
Se isto parece confuso, deixa-me dar alguns exemplos familiares:
-
O tipo
booleané o conjunto de todos os booleanos (existem apenas dois:trueefalse) e as operações que podes efetuar sobre eles (como||,&&, e!). -
O tipo
numberé o conjunto de todos os números e as operações que podes realizar sobre eles (como+,-, *,/,%,||,&&, e?), incluindo os métodos que podes chamar sobre eles como.toFixed,.toPrecision,.toString, e assim por diante. -
O tipo
stringé o conjunto de todas as cadeias de caracteres e as operações que podes efetuar sobre elas (como+,||, e&&), incluindo os métodos que podes chamar sobre elas, como.concate.toUpperCase.
Quando vês que algo é do tipo T, não só sabes que é um T, como também sabes exatamente o que podes fazer com esse T (e o que não podes). Lembra-te, o objetivo é usar o verificador de tipos para te impedir de fazer coisas inválidas. E a forma como o typechecker sabe o que é válido e o que não é é olhando para os tipos que estás a utilizar e como os estás a utilizar.
Neste capítulo, faremos um tour pelos tipos disponíveis no TypeScript e abordaremos o básico do que podes fazer com cada ...
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.