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Liam McLennan hackingon.net

This post is part of a series comparing the language features of the C#, Javascript and Ruby programming languages.

Variables

C# requires that variables be declared with a specific type. Javascript and Ruby determine the type of variables at runtime. Here is the syntax:

C#

public string publicMessage = "Hello World";
private string privateMessage = "Hello World";
static string PRIVATE_MESSAGE = "Hello World";

Javascript

var message = "Hello World";

Javascript does not have a syntax for making variables public or private, instead it is achieved by a clever usage of closure (discussed later). Javascript does not have block scope, which means that variables defined within a block can be accessed from outside the block (a block is anything in {} such as and if statement or a loop). In Javascript variables are scoped to the function in which they are declared and are visible anywhere within that function, including within inner functions.


// this function will alert "Hello World" twice.
function showMessage() {

  if (true) {
    var message = "Hello World";
  }
  
  alert(message);
  
  var innerFunction = function() {
    alert(message);
  };
  
  innerFunction();
}

Ruby

A ruby variable is declared by assigning to the variable name. Ruby uses prefixes to indicate the variable scope.

# local variable
message = "Hello World"

# instance variable
@message = "Hello World"

# static variable
@@message = "Hello World"

# global variable
$message = "Hello World"
Posted on Monday, November 23, 2009 4:13 PM | Back to top

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