PhantomJS includeJS()

var wpage = require('webpage').create(); 
wpage.includeJs(jsfile,function(){});

var wpage = require('webpage').create();  
wpage.onConsoleMessage = function (str) { 
   console.log('CONSOLE: ' + msg); 
} 
wpage.open('http://localhost/tasks/a.html', function(status) { 
   wpage.includeJs('http://localhost/tasks/testscript.js', function() { 
      var foo = wpage.evaluate(function() { 
         return testcode(); 
      }); 
      console.log(foo); 
   }); 
});

function testcode () { 
   return "welcome to phantomjs"; 
}

welcome to phantomjs