检查该功能是否已启动javascript

Question

is there any idea how I can check whether it is already added this script on the page.

function init(){

var script   = document.createElement("script");
script.type  = "text/javascript";
script.text  = 'setTimeout(function(){ alert("test msg") }, 10000);';
document.body.appendChild(script);

}

NOTE: I want you to run one function until after it no longer runs.

Answer 1

I got confused in the title you ask for a solution if the function is called and in you message you ask for a solution to check if the script exists already on the page. So I solved both.

1) know when the script has completed loading and started running your script:

function init(callback){
  var script   = document.createElement("script");
  script.type  = "text/javascript";
  script.text  = 'setTimeout(function(){ alert("test msg") }, 10000);';
  script.onload = callback;
  document.body.appendChild(script);
}

init(function(e){
  console.log('script loaded.',e);
});

2) check if the script was already added to the dom

function init(){
  var script   = document.createElement("script");
  script.type  = "text/javascript";
  script.text  = 'setTimeout(function(){ alert("test msg") }, 10000);';
  var checkExistance = document.scripts.filter(function(v){ return v.isEqualNode(script) });
  var exists = checkExistance.length>0;
  if(!exists) document.body.appendChild(script);
}

3) combine them if you want... The callback won't be called if the script exists already since the file starts loading as soon as it's added to the DOM.

function init(callback){
  var script   = document.createElement("script");
  script.type  = "text/javascript";
  script.text  = 'setTimeout(function(){ alert("test msg") }, 10000);';
  script.onload = callback;
  var checkExistance = document.scripts.filter(function(v){ return v.isEqualNode(script) });
  var exists = checkExistance.length>0;
  if(!exists) document.body.appendChild(script);
}

init(function(e){
  console.log('script loaded.',e);
});