How to Dynamically load JavaScript Source files to a webpage 
//Create a 'script' element	
var scrptE = document.createElement("script");

// Set it's 'type' attribute	
scrptE.setAttribute("type", "text/javascript");

// Set it's 'language' attribute
scrptE.setAttribute("language", "JavaScript");

// Set it's 'src' attribute
scrptE.setAttribute("src", "myjsfile.js");

// Now add this new element to the head tag
document.getElementsByTagName("head")[0].appendChild(scrptE);