外部JavaScript渲染

Question

There are two javascript files on a page, both coming from different domains. Now the 2nd file is loaded before the 1st as the server response time for the 2nd javascript file is greater than for the first javascript file. The second javascript file depends on some function set in the first javascript file, so it is throwing an error.

Now my question is: does javascript file ordering take place? ie do they execute sequentially? If yes, then why is the second javascript file executed first and throws an error

Answer 1

If you have script elements they will execute in the order they are placed, unless you load them programmatically or explicity tell them to load asynchronously with the HTML5 async attribute (which is not supported by IE less than version 10).

It is possible that the scripts themselves have asynchronous behavior inside of them, which could cause the appearance of them executing in the wrong order.

Answer 2

If you are loading two scripts via AJAX, then have two functions (one to load each) and call the second one when the first has loaded. Like so (below is just an example):

function loadfirstscript()
{
var http = new XMLHttpRequest();
var url = "get_data.php";
http.open("GET", url, true);

http.onreadystatechange = function() {//Call a function when the state changes.
     if(http.readyState == 4 && http.status == 200) {
          //do something here...

          loadsecondscript() //Call the second script
     }
}
http.send(params);
}

Edit: Sorry if this does not answer your question, but I am not too sure what you are asking if this does not answer your question.