Untitled

<script type="text/javascript" src="file1.js"></script>
<script type="text/javascript" src="file2.js"></script>

function primary()
{
    secondary();
}

function secondary()
{
    alert("hi primary");
}

<html>
<head>
<script src=script1.js></script>
<script src=script2.js></script>
</head>
<body>
</body>
</html>

secondary();

secondary();

<html>
<head>
<script src=script1.js defer></script>
<script src=script2.js></script>
</head>
<body>
</body>
</html>

$.getScript("file1.js",function(){

    alert("File1.js is loaded");
}

File1 = function(){
}
File1.prototype=
{
    constructor:File1,
    primary:function()
    {
        if (File2 == "undefined")
        {
           $.getScript("file2.js",function()
           {
              file2 = new File2();
              file2.secondary();
           });
        }
    }
}

File2 = function(){
}
File2.prototype=
{
  constructor:File2,
  secondary:function()
  {
    if (File1 == "undefined")
    {
      $.getScript("file1.js",functiom()
      {
         file1 = new File1();
         file1.primary();
      });
    }
  }
}