JavaScript Tutorial/Language Basics/Variables

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Assign one variable to another variable

   <source lang="javascript">

<html> <head> <title>A Simple Page</title> <script language="javascript">

</script> </head> <body> </body> </html></source>


Braces indicate code blocks

Code blocks indicates a series of statements that should be executed in sequence.

Code blocks are enclosed between an opening brace ({) and a closing brace (}).



   <source lang="javascript">

if (test1 == "red") {

  test1 = "blue";
  alert(test1);

}</source>


Declare two variables in the same line

   <source lang="javascript">

<html> <head> <title>A Simple Page</title> <script language="javascript">

</script> </head> <body> </body> </html></source>


Define variable and assign value

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<html> <head> <title>Variable Demo</title> <script language="javascript" type="text/javascript">

</script> </head> <body>

Variable Demo

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Do simple calculation

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<HTML> <BODY> <SCRIPT language="JavaScript">

</SCRIPT> </BODY> </HTML></source>


Naming Variables

The first character of the name must be a letter or an underscore (_).

All characters following the first character can be letters, underscore, or digits.

Letters can be either upper or lowercase.

JavaScript does distinguish between the two cases.

All the following variable names are legal:



   <source lang="javascript">

var test; var $test; var $1; var _$te$t2;</source>


Reassigning value to Variables

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<html> <head> <title>Reassigning Variables</title> <script language="javascript" type="text/javascript">

</script> </head> <body>

Reassigning Variables

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Reference a variable without declaration

   <source lang="javascript">

<html> <head> <title>A Simple Page</title> <script language="javascript">

</script> </head> <body> </body> </html></source>


Variables

Variables in JavaScript are defined by using the var operator (short for variable), followed by the variable name, such as:



   <source lang="javascript">

var test = "hi";</source>


Variables can hold different types of values at different times

A variable can be initialized with a string value, and later on be set to a number value.



   <source lang="javascript">

var test = "hi"; alert(test); test = 55; alert(test);</source>


Variables don"t have to be declared before being used

When the JavaScript sees a declared identifier (var varName), it creates a global variable.



   <source lang="javascript">

var sTest = "hello "; sTest2 = sTest + "world"; alert(sTest2);</source>


Working With JavaScript Variables

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<HTML> <HEAD> <TITLE> Working With JavaScript Variables </TITLE> </HEAD> <BODY>

Working With JavaScript Variables

<SCRIPT LANGUAGE="JavaScript">

</SCRIPT> </BODY> </HTML></source>