让JavaScript和其它资源并发下载的方法

head.js("/path/to/jquery.js", "/google/analytics.js", "/js/site.js", function() { 
  // all done 
}); 
  
// the most simple case. load and execute single script without blocking. 
head.js("/path/to/file.js"); 
  
// load a script and execute a function after it has been loaded 
head.js("/path/to/file.js", function() { 
  
}); 
  
// load files in parallel but execute them in sequence 
head.js("file1.js", "file2.js", ... "fileN.js"); 
  
// execute function after all scripts have been loaded 
head.js("file1.js", "file2.js", function() { 
  
}); 
  
// files are loaded in parallel and executed in order they arrive 
head.js("file1.js"); 
head.js("file2.js"); 
head.js("file3.js"); 
  
// the previous can also be written as 
head.js("file1.js").js("file1.js").js("file3.js");