How does JavaScript Variable Scope work?

Javascript Web Development Front End Technology

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

Global Variables − A global variable has a global scope which means it can be defined anywhere 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.

Let’s see how the scope of variables works in JavaScript.

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.

Example

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

Ali

Published on 16-Jan-2018 10:45:25

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