包括外部javascript文件

Question

I am trying to include external javascript to a document. Let's say that external js has the following code.

function myFunction() {
  console.log("hello");
}

and I include it from console by

var script = document.createElement('script');
script.src = "http://myjs";
document.getElementsByTagName('head')[0].appendChild(script);

but then I still get myFunction() is undefined error. The function is being called from php file included on the page somehow. Interestingly, appending my external javascript right after the head tag in the document was not enough for it to precede the function call from the loaded php file.

Q: how do I ensure that I include my javascript BEFORE the php file given my situation?

EDIT: this is the hierarchy of all the sources

mysubsite.com
  myfolder
    mypage.html

mysite.com
  myfolder
    main.php
    problem.php

problem.php is calling function myFunction() but it's not included anywhere yet. So I try to define the function in an outside js file and include it in mypage.html, but problem.php still comes before the included javascript in mypage.html

EDIT:

I think the real problem is that I am dealing with an iframe that's included inside a main document. In this case, is there a way to include my external javascript file inside the main document from console? Including scripts from console only affects the iframe instead of the main document.

Answer 1

What you're doing is fine, but then you have to wait for the file to load. Most browsers will raise the load event on the script element although some older versions of IE use onreadystatechanged instead. But since you're using jQuery (from the tags on the question), you don't have to worry about that, you can just use $.getScript :

$.getScript("http://myjs", function() {
    // The script has been loaded, you can call myFunction now
});

Answer 2

PHP is always included before JavaScript. PHP is executed by the server before it's sent to the client, and JavaScript is executed by the client.

Why can't you just put a regular <script type="text/javascript" src="http:/myjs"></script> in your head ?