Dynamic Script Elements 动态脚本元素

loadScript.js

function loadScript(url, callback){
  var script = document.createElement ("script") ;
  script.type = "text/javascript";

  if (script.readyState){ //IE
    script.onreadystatechange = function(){
      if (script.readyState == "loaded" || script.readyState == "complete"){
        script.onreadystatechange = null;
        callback(); 
      }
    };
  } else { //Others
    script.onload = function(){ callback(); }; 
  }
  script.src = url;
  document.getElementsByTagName("head")[0].appendChild(script); 
}

loadScript("file1.js", function(){  //调用
  alert("File is loaded!"); 
});