gistfile1.js

window.onload = function () {                             
  var loadScript = function (scriptUrl, callback) {       
    var script = document.createElement("script");        
    script.src = scriptUrl;                               
    script.onload = callback;                             
    document.body.appendChild(script);                    
  };                                                      
                                                          
  loadScript("http://localhost:3002/a.js", function () {  
    loadScript("http://localhost:3002/b.js", function () {
      console.log(A());                                   
      console.log(B());                                   
    });                                                   
  });                                                     
};