JavaScript

JavaScript refers to the behavior of web pages.

W3 Schools JS

    Resumo:
    • Javascript is a dynamically typed language, meaning that it's engine figures out the value of a variable at run time.
      • This allows variables to change such as from a number to a char.
    • Functions can be global (where it's results will be available to the entire page) or locally.
      Locally: when you create a variable inside a function, it only exists there.

    Types
    • Used to build other data structures.
    • JS has 7 built-in types: 6 primitive and 1 Object type.

    • Object type: a collection of name/value pairs.
      • Ex: firstName: Noah (firstName is the name and Noah is the value being atributed to that name).

    • Primitive type: represents a single, immutable value:
      Single value, therefore, not an object.
      Immutable means once it's set, it can not be changed.
       * Value becomes read only.
       * You can create another value based on an existing one.

    • Usually you put .js files that require the whole content of the page to be loaded first on the bottom of the codding.
      Assim, quando chamar o elemento, por exemplo console.log('title'), para mostrar o title da pagina, ja vai ter sido carregado, being that if the script was at the top, it wouldn't know the title.

    What is JavaScript ?
    • JavaScript is:
      a) Lightweight: doesn't consume much memory of the computer and it has a simple syntax and features.
      b) Crossplaform: means that the language can be used on multiple plataforms and systems, not only for webdevelopment.
      c) Object-oriented: it's a language based on objects.

    • Today, JavaScript can be used in different places:
      Client-side: JavaScript was traditionally only used in the browser.
      Server-side: Thanks to node.js, we can use JavaScript on the server as well.

    • Made modern development possible:
      a) Dynamic effects interactivity (adicionar efeitos a simples websites).
      b) Modern web applications that we can interact with.

    • Data Types
      a) Numbers: float, int (but here all numbers are treated as float).
      b) String: text.
      c) Boolean: true, false.
      d) Undefined: variable declared on the script but no value was attributed to it.
      Example: var job;
      e) Null: variable defined but empty, no values in it.

    • Code
      \b - backspace
      \f - form feed
      \n - new line
      \r - carriage return
      \t - Tabulação horizontal
      \v - tabulação vertical
      \' - aspas simples
      \" - aspas duplas
      \\ - barra invertida

      \XXX - caractere no formato Latin-1 (XXX é um valor octal entre 0 e 377)
      \xXX - caractere no formato Latin-1 (XX é um valor hexadecimal entre 00 e FF)
      \uXXXX - caractere no formato Unicode, especificado por um valor hexadecimal de 4 dígitos. O navegador deve suportar Unicode e o sist.op. deve ter as fontes instaladas para que os caracteres sejam visualizados.