JavaScript Tutorial #7 – Variables and Datatypes

The developers can use the following primitive datatypes in their web application or Windows store application.

– String

– Boolean

– Numbers

JavaScript also support null and undefined.

The variables are like containers that can hold data . The data can be accessed by specifying the variable name. The variable in JavaScript are declared using var keyword. The developers can initialize the variable with a value either during the variable initialization or later in the program.

Below is a sample program demonstrating the usage of variables of various datatypes in JavaScript.

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <title>Ginktage.com Home Page</title>
    <script language="javascript" type="text/javascript">
        var TutorialName = "Ginktage.com - Learn JavaScript";
        var Salary  = 10000.50;
    </script>
</head>
<body>
</body>
</html>

The var keyword has a purpose . Javascript language is kind of untyped language . You don’t have to specify the type of variable during the declaration . Javascript takes care of the type automatically based on the values assigned.

The JavaScript variable can either have a Global scope or local scope . A global scoped variable is accessible everywhere in your javascript file but a local scoped variable is only visible within the function where it is defined.

Below is a sample code snippet demonstrating the Global scope and local scope variable.

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <title>Ginktage.com Home Page</title>
    <script type="text/javascript">
    var Variable1 = "Ginkatge.com"; // Global Variable
    function checkscope() {
        var Variable1 = "Google.com";  // Local Variable
    }
    </script>

</head>
<body>
</body>
</html>

There are some rules to be followed when declaring a variable in JavaScript.

  • The variable name should not have any reserved keyword of JavaScript.
  • The variable name should not start with a number . It should begin with a letter or underscore . Also note that it is case sensitive.
  • Eg : _Test1 is a valid variable name.
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