JavaScript Variable Scope

The scope of a variable is the region of your program in which it is defined. JavaScript variable will have only two scopes.

• Global Variables: A global variable has global scope which means it is defined everywhere in your JavaScript code.
• Local Variables: A local variable will be visible only within a function where it is defined. Function parameters are always local to that function.

Within the body of a function, a local variable takes precedence over a global variable with the same name. If you declare a local variable or function parameter with the same name as a global variable, you effectively hide the global variable. Following example explains it:

<script type="text/javascript"> <!-- var myVar = "global"; // Declare a global variable function checkscope( ) { var myVar = "local"; // Declare a local variable document.write(myVar); } //--> </script>

This produces the following result:

local