17 Functions.html

<html lang="en">
    <head><title>Functions</title>
    <!--
        A JavaScript function is a block of code designed to perform a particular task.
        A JavaScript function is executed when "something" invokes it (calls it).
        A JavaScript function is defined with the function keyword, followed by a name, followed by parentheses ().
        
        Functions also help in keeping the code more updatable and more organise
    
        Why to use Functions?
            You can reuse code: Define the code once, and use it many times.
            You can use the same code many times with different arguments, to produce different results.
   
    -->
    </head>
  
    <body>
        
        <script type="text/javascript">
         //defining the function
         function display(){
            alert("Function Called");
         }
         display(); // calling the function // here when you open the webpage its going to call it
        
        //finding average of two numbers
        //average formulla (x+y)/2
         function average(a,b){
            return ((a+b)/2); // or return (a+b)/2;
         }
         var x=4;
         var y=5;
         //calling the average function
         document.write(average(x,y)); // also displaying the return value of function and calling it also
        
        </script>
    </body>
</html>